Graphite Oxide Nanocomposites Research Articles

Reforming of graphite oxide from agro-waste by incorporating nanosilica for the remediation of nitrate and phosphate anions from wastewater

Graphite oxide obtained from the oxidation of sawdust with (0.5 wt%) was immobilized into silica to improve the effectiveness of the silica phase toward depollution. The functional interaction profiles were assessed using XRD and SEM performances. The excess loading of graphite oxide percent encouraged the aggregation of incorporated silica molecules, forming the so-called “colonies”. Such colonies caused marked exfoliation of graphite oxide layers in the as-designed silica @graphite oxide hybrid materials and considerable coalescence of graphite oxide in a silica matrix. The as-designed silica @(0.01) graphite oxide nanocomposites showed pronounced sorption competencies for PO4-3 (95 %), not the same for NO3– (72 %). Such depollution behavior is governed by the interaction profiles including the incorporated graphite oxide and “silica colonies”. The fitness of the kinetic models was ranked as pseudo-first order. The values of ΔHo = 0.824 and 3.58, So = 0.109 and 0.116, and Go = –33.45 to −36.7 kJ/mole for phosphate and nitrate, respectively. The estimated data point to endothermic, spontaneous adsorption in nature.

Synthesis of metal–organic nanofiber/rGO nanocomposite as the sensing element for electrochemical determination of hypoxanthine

Abstract In this study, metal–organic nanofibers (MONFs) and reduced graphite oxide (rGO) nanocomposite were used to modify the surface of glassy carbon electrode, and the electrochemical sensor was applied to the differential pulse voltammetry determination of hypoxanthine, the oxidation intermediate of human purine degradation metabolism. The preparation of MONFs/rGO nanocomposite is simple, efficient, and environmentally friendly. The morphology and structure of MONFs/rGO nanocomposite were characterized by field emission scanning electron microscopy and X-ray diffraction. The results show that the improved sensor has a significant increase in current density, with linear ranges of 0.1–10 and 20–100 μM. Detection limit 0.01 μM (S/N = 3). Under the optimized conditions, the improved sensor shows very good stability, selectivity, and improved accuracy.

Insight into a pure spinel Co3O4 and boron, nitrogen, sulphur (BNS) tri-doped Co3O4-rGO nanocomposite for the electrocatalytic oxygen reduction reaction.

The intricate problems concerning energy require innovative solutions. Herein, we propose a smart composite nano system that can be used in a sustainable and dichotomous manner to resolve energy crises. The current study describes a new way to synthesize a pure spinel cobalt oxide (Co3O4) and boron (B), nitrogen (N), and sulfur (S) tri-doped Co3O4-reduced graphite oxide (rGO) nanocomposite (CBNS). A hydrothermal method has been used for the synthesis of these nanomaterials. The synthesized nanocomposite was characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). The XRD results showed the formation of Co3O4 and B, N, S doped nanocomposite with high purity and crystallinity. XAS analysis elucidates the formation of spinel Co3O4 with tetrahedral and octahedral arrangement of cobalt ions. The peaks at 2.50 Å and 3.07 Å are due to the Co-Co bonding. The electrocatalytic oxygen reduction (ORR) was successfully implemented using these nanocomposites. The electrochemical study exhibits the better activity of the B, N, and S tri-doped Co3O4-rGO nanocomposite due to the mutual effect of B, N and S. The synthesized catalyst has maximum current density of 9.97 mA cm-2 with onset potential (Eonset) of 0.98 V in alkaline medium.

The Impact of Graphite Oxide Nanocomposites on the Antibacterial Activity of Serum.

Nanoparticles can interact with the complement system and modulate the inflammatory response. The effect of these interactions on the complement activity strongly depends on physicochemical properties of nanoparticles. The interactions of silver nanoparticles with serum proteins (particularly with the complement system components) have the potential to significantly affect the antibacterial activity of serum, with serious implications for human health. The aim of the study was to assess the influence of graphite oxide (GO) nanocomposites (GO, GO-PcZr(Lys)2-Ag, GO-Ag, GO-PcZr(Lys)2) on the antibacterial activity of normal human serum (NHS), serum activity against bacteria isolated from alveoli treated with nanocomposites, and nanocomposite sensitivity of bacteria exposed to serum in vitro (using normal human serum). Additionally, the in vivo cytotoxic effect of the GO compounds was determined with application of a Galleria mellonella larvae model. GO-PcZr(Lys)2, without IR irradiation enhance the antimicrobial efficacy of the human serum. IR irradiation enhances bactericidal activity of serum in the case of the GO-PcZr(Lys)2-Ag sample. Bacteria exposed to nanocomposites become more sensitive to the action of serum. Bacteria exposed to serum become more sensitive to the GO-Ag sample. None of the tested GO nanocomposites displayed a cytotoxicity towards larvae.

High‐frequency measurement of dielectric permittivity and antimicrobial properties of polyaniline and graphite oxide nanocomposites

The polyaniline/graphite oxide (PANI/GO) nanocomposite was prepared by the in situ chemical polymerisation method. The synthesis involved the formation of dark green coloured polyaniline/graphite oxide composite. The crystalline structure and morphology of the composite were studied using UV-visible spectroscopy (UV), X-ray diffraction (XRD) and transmission electron microscopy (TEM).The characteristic peaks in XRD and UV-visible spectra confirmed the formation of the PANI/GO nanocomposite. DC conductivity measurements were performed using a two-probe method. Dielectric responses of the composites were investigated in the frequency range100 MHz to 3 GHz by the RF impedance analyser. The dielectric constant ϵ′(w) and dielectric loss ϵ′′(w) were investigated. It was observed that the dielectric constant ϵ′(w) and dielectric loss ϵ′′(w) decreased with an increase in frequencies (for different wt % of GO). The antibacterial activity of this composite was examined.

Thermal reduction of graphite oxide in the presence of nitrogen-containing dyes

Thermal reduction of graphite oxide (GO) is considered as a prospective method for the preparation of high-performance graphene-based materials. However, this method has certain limitations, and the major is that this exothermic process is difficult to control. In this research, we focused on the kinetic studies of the reduction of graphite oxide using non-isothermal differential calorimetry (DSC) method. Six GO nanocomposites with dyes were tested to study the shift in kinetic parameters. The apparent reaction order is determined to be ca 0.7 for the thermal decomposition of pure GO, while in the presence of dye molecules it increases sometimes reaching a value of 2.0 for higher dye concentrations. Decisively, the thermal decomposition of pure GO can be presented as an intermediate between a zero- and first-order reaction, while the introduction of dye molecules turns a certain part of the energy consumption via the bimolecular pathway. Our research revealed that the process of GO thermal decomposition can be operated and properties of the final product (reduced graphene oxide (rGO) and its derivatives) can be adjusted more precisely using additive molecules, which interact with GO sheets.

Synergistic Effect of High-Performance N,S–TiO2/N,S–RGO Nanocomposites for Photoelectrochemical Water Oxidation

Nitrogen and sulfur codoped mesoporous anatase–brookite biphasic TiO2 anchored on surface of nitrogen and sulfur codoped reduced graphite oxide nanocomposites (N,S–TiO2/N,S–RGO) were easily prepared via a simple hydrothermal reaction process. XRD and Raman revealed anatase and brookite mixed phases. Also, the selected area electron diffraction (SAED) and the fast Fourier transform (FFT), from HRTEM measurements, indicated the presence of the anatase and brookite two phases. XPS showed the incorporation of N and S in both TiO2 matrix and carbon framework structure of RGO. The N,S–TiO2/N,S–RGO photoanodes exhibited an excellent photoelectrochemical (PEC) water oxidation performance. The highest photocurrent density reached 1.1 mA cm−2 for the N,S–TiO2/N,S–RGO(0.1) nanocomposite photoanode which is 6 times enhancement greater than bare TiO2 and 5 times enhancement than the N–TiO2/N–RGO(0.1) (the same GO ratio) at the same potential. These are considered significant promising results in comparison with our previous reported S–TiO2/S–RGO nanocomposite which revealed only 3 times enhancement in photocurrent density than bare TiO2.

Synthesis of nanocomposites using xylan and graphite oxide for remediation of cationic dyes in aqueous solutions

Due to the rapid development of industrialization, the water resources on which we depend are facing unprecedented challenges. Dyes, as an indispensable substance in our lives, have caused great pollution to the water resources in nature, and the removal of dyes from wastewater is becoming an important topic. A porous xylan/poly(acrylic acid)/graphite oxide nanocomposite was prepared by graft polymerization and used for adsorption of cationic ethyl violet dye in wastewaters in this paper. Various techniques, i.e., Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, elemental analysis, scanning electron microscopy, and ultraviolet-visible spectroscopy, were used to study this composite. Adsorption isotherm measurements showed that the composite's adsorption behavior fits the Langmuir isotherm adsorption model. Adsorption tests showed that this material has excellent adsorption properties; the maximum adsorption capacity for ethyl violet dye was 273.99 mg/g. Investigation of the adsorption mechanism indicated that electrostatic forces and π–π effects are mainly involved in adsorption. Desorption cycling tests showed that the adsorption efficiency of the composite was still over 95% after 3 cycles. These results show that this porous xylan/poly (acrylic acid)/graphite oxide nanocomposite has potential applications in cationic dye removal.

Nitrogen-doped carbon-coated Fe3O4/rGO nanocomposite anode material for enhanced initial coulombic efficiency of lithium-ion batteries

Nitrogen-doped carbon-coated Fe3O4/reduced graphite oxide (NC@Fe3O4/rGO) nanocomposites with in situ polymerized melamine-formaldehyde resin (MFR) as the carbon sources were synthesized via the decomposition of MFR/Fe3O4/rGO nanocomposites. Fe3O4 NPs were embedded in the integrated carbon matrix composed of protective carbon layer and conductive rGO sheets offering excellent buffer effect. The NC@Fe3O4/rGO nanocomposites were tested as anode materials for lithium-ion batteries (LIBs) and displayed a large reversible specific capacity of above 900 mA h g−1 after 100 cycles at a current density of 50 mA g−1, high coulombic efficiency (~ 98%) with an initial coulombic efficiency of 86%. The high initial coulombic efficiency is critical for the practical application of the transition metal oxide–based anode materials.

Excellent Microwave Absorption Properties Derived from the Synthesis of Hollow Fe₃o₄@Reduced Graphite Oxide (RGO) Nanocomposites.

Magnetic nanoparticles, such as Fe3O4 and Co3O4, play a vital role in the research on advanced microwave absorbing materials, even if problems such as high density and narrow band impedance matching are still unsolved. Herein, the study of lightweight hollow Fe3O4@reduced graphite oxide (RGO) nanocomposites synthesized via the solvothermal method is presented. The microstructure and crystal morphology of the materials were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. Single crystalline hollow Fe3O4 spheres were grown onto RGO flakes, leading to the formation of heterojunction, which further influenced the microwave absorption properties. The latter were evaluated by standard microwave characterization in the frequency range of 2–18 GHz. It was found that, for a specific Fe3O4@0.125 g RGO composite, the minimum reflection loss can reach −41.89 dB at 6.7 GHz, while the reflection loss was less than −10 dB from 3.4 GHz to 13.6 GHz for a nanocomposite sample thickness in the range of 1–4 mm. The combination of these two materials thus proved to give remarkable microwave absorption properties, owing to enhanced magnetic losses and favorable impedance matching conditions.

High Catalytic Activity of W18 O49 Nanowire-Reduced Graphite Oxide Composite Counter Electrode for Dye-Sensitized Solar Cells

The W18O49 nanowire (NW)-reduced graphite oxide (W18O49-rGO) nanocomposite was prepared by a facile solvothermal reaction. The W18O49 NWs were stably dispersed on the surface of rGO, and the content of W18O49 NWs in the composite can be tailored by controlling the mass ratio of reactants (WCl6 and graphite oxide). Employing the W18O49-rGO nanocomposite with the proper W18O49 NW content of 33% as a counter electrode of dye-sensitized solar cells (DSSCs), it gets a photoelectrical conversion efficiency (η) of 7.23%, which is close to that of Pt-based DSSC (7.39%). The high efficiency of DSSCs based on W18O49-rGO counter electrode is contributed to the intrinsic electrocatalytic activity of W18O49 NWs and excellent electron-transfer characteristics of rGO. The first-principles calculations have been first employed to investigate the adsorption energy between I3− molecule and W18O49 NW to explain its good catalytic activity. The cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and Tafel polarization tests can further identify that the W18O49-rGO counter electrode has high electrocatalytic activity for the reduction of I3− and low interface charge transfer impedance. It is believed that the W18O49-rGO nanocomposite can be used as a promising counter electrode material for DSSCs.

Preparation and characterization of graphite oxide nano‐reinforced biocomposites from chicken feather keratin

AbstractBACKGROUNDNatural polymers have gained increased attention in reducing the dependence on petroleum‐based materials. Chicken feather proteins are an abundant industrial by‐product suitable for the fabrication of sustainable thermoplastics. However, protein‐based plastics generally exhibit poor physical and thermal properties which limit their application.In this research, the fabrication of feather keratin based nano‐reinforced biocomposites by the addition of graphite oxide (GO) in a reactive extrusion system were investigated. The effects of GO carbon/oxygen ratio (C/O, 2.48, 2.07, and 1.55) and concentration (0.5–2%) of the selected GO on the conformational, physical and thermal properties of thermoplastic films were investigated.RESULTSChicken feather–GO nanocomposites were successfully prepared at 150 °C in the reactive extrusion system. Tensile strength and Young modulus of chicken feather plastic films were significantly increased without affecting their elongation using low GO concentrations (0.5 to 1.5% w/w of protein). Our results suggest that higher content of hydroxyl groups and increased graphene interlayer space in GO facilitated interactions with feather keratin and plasticizers.CONCLUSIONSGraphite oxide proved to be an inexpensive alternative to graphene for the reinforcement of protein based composites. Extrusion provided a cost‐effective and environment‐friendly method for the processing of sustainable composites. © 2017 Society of Chemical Industry

Unveiling the thermal kinetics and scissoring mechanism of neolatry polyethylene/reduced graphite oxide nanocomposites

The present study focuses on thermal degradation mechanism of low density polyethylene (LDPE)/reduced graphite oxide (rGO) nanocomposites prepared by solvent cast method with an implication of its kinetics modelling. Graphite oxide (GO) was reduced under solvothermal conditions, using sodium borohydride and 0.1, 1.0, 3.0 and 5.0wt% of rGO was incorporated into LDPE. Thermogravimetric analysis (TGA) was used to determine the decomposition kinetics of the nanocomposites at different heating rates of 1, 5, 10 and 20°C/min. The maximum activation energy (Ea) calculated using Kissinger (K) and Flynn-Wall-Ozawa (FWO) models were noted to be 321.80 and 335.01kJ/mol respectively at nanocomposite with 3wt% rGO content. Also, the correlation coefficient (r2) in FWO models was higher than 0.95, confirming a single-step decomposition in the nanocomposites. TGA coupled with gas chromatography (GC) and mass spectroscopy (MS) was employed to separate the evolved compounds into alkane, alkene and aromatic groups. Interestingly, pravastatin, a useful gaseous compound was detected at 370°C and other toxic gases were evolved at degradation temperature ∼460°C and above. Our findings on kinetics behaviour and degradation mechanism emphasize on the thermal cracking characteristic of the LDPE/rGO nanocomposites, which can be utilized to extract useful gaseous components for pharmaceutical application.

Polypyrrole@MoO3/reductive graphite oxide nanocomposites as anode material for aqueous supercapacitors with high performance

A nanocomposite of polypyrrole@MoO3/reduced graphene oxide (PPy@MoO3/rGO) as anode material for supercapacitors was fabricated by a facile and green route. Cyclic voltammograms, charge/discharge profiles, and AC impedance measurements indicated that the kinetics performance of PPy@MoO3/rGO is better than that of PPy@MoO3 nanocomposite. The ternary nanocomposite delivers a higher specific capacitance of 175Fg−1 at 100mAg−1 and better cycling behavior with capacity retention ratios of 88% after 600 cycles compared to the PPy@MoO3 nanocomposite.

Polyethylene/reduced graphite oxide nanocomposites with improved morphology and conductivity

The use of graphite and polyolefins as starting materials to prepare nanocomposites is convenient because both are inexpensive and have very different properties, one is conductive and the other is insulating. The formation of nanocomposites can extend the applicability of both commodities. In this work we synthesized nanocomposites of polyethylene (PE) with two types of graphites, graphite oxide (GO) and reduced graphite oxide (RGO), by in situ polymerization using a supported metallocene catalyst. The functional groups on the graphites were used to support the metallocene catalyst by a previous treatment with methylaluminoxane. The nanocomposites were obtained with good catalytic activities and presented excellent morphology and dispersion; their elastic modulus and crystallization temperatures were higher than those of neat PE. However, the nanocomposites PEGO were insulant, whereas PERGO had a conductivity of 1.1 × 10−5 S cm−1 with 3.1 wt% filler. This is a significant result compared to the conductivity obtained using non-supported graphite nanosheets where more than 15 wt% of graphite nanosheets are needed to obtain conductivities higher than 10−7 S cm−1. This improvement in the percolation threshold was attributed to the good morphology of the PERGO nanocomposites obtained due to the control of the graphitic sheets and the support methodology.

Investigation on Relaxational Behavior of Alkylammonium Ions Intercalated in Graphite Oxide

Graphite oxide (GO) nanocomposites have been synthesized to contain various concentrations of intercalated alkylammonium ions and characterized with X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and differential scanning calorimetry. Depending on their concentration, the alkyl chains may lie parallel to the GO plane one or two layers thick or they form two columns inclined at an angle ∼37° to the plane. Dielectric spectroscopy reveals a relaxation process far below room temperature, attributed to small-angle wobbling around the long molecular axis. The activation energy of this relaxation increases as the intercalate changes from one to two layers, and to dual columns, with increasing interactions among the intercalated molecules. An additional phase transition occurs in composites with high concentrations of intercalate between a rotator-type solid phase to a disordered phase for the confined alkyl chains.

Magnetic Solid Phase Extraction Coupled with HPLC Towards Removal of Pigments and Impurities from Leaf-derived Paclitaxel Extractions of Taxus baccata and Optimization via Response Surface Methodology

A reusable and cost-effective magnetic graphite oxide (Fe3O4NPs@GO) nanocomposite was fabricated and applied for pre-purification of paclitaxel from leaf-derived crude extract of Taxus baccata. Furthermore, the potential roles of three crucial criteria (i.e., adsorbent dosage, sorption temperature and agitation/shaking power) on the two responses [i.e., efficiency of plant pigments removal (EPPR) and efficiency of taxol purity (ETP)] were examined and simultaneously optimized through response surface methodology. The nanocomposite was accurately characterized using TEM, AFM, BET, FT-IR, Raman and VSM. Moreover, for both proposed second-degree polynomial regression models, highly significant correlations were achieved between the experimental and predicted data (p < 0.0001). Meanwhile, the optimum conditions to simultaneously acquire the maximum EPPR (94.0 %) and ETP (11.4 %) were recorded as adsorbent dosage of 37.7 g L−1, sorption temperature of 30.7 °C and agitation power of 153.1 rpm; and the predictive results were confirmed using experimental rechecking survey. Interestingly, upon five consecutive treatments, the nanocomposite still exhibited substantial potency in eliminating large amounts of plant pigments and impurities (up to 90 %), without significant reduction on sorption capacity and magnetism thereof. Our results demonstrated that the current nanocomposite, as SPE sorbent for MSPE, could be a simple, fast and reusable approach for HPLC-based purification studies of paclitaxel, and probably other plant secondary metabolites.

Size and Dispersion Control of Pt Nanoparticles Grown Upon Graphite-Derived Nanosheets

Graphite oxide (GO) nanosheets, graphene nanosheets (GNS), and nanocomposites comprising of GO or GNS coated with polypyrrole (PPy) were prepared and assessed for their ability to influence the surface deposition and growth of Pt nanoparticles. GO was obtained from graphite via oxidation and exfoliation, and GNS was obtained from GO in a subsequent reduction. Both GO and GNS were coated with PPy via in situ polymerization of pyrrole (Py), forming surface-enhanced materials. Scanning electron microscope, energy-dispersive x-ray, transmission electron microscopy, electron energy loss spectroscopy, Raman, and atomic force microscope findings showed that the Pt nanoparticle loading, agglomeration size, aggregate morphology, and surface dispersion varied according to the nanosheet surface, nanocomposite type, and Py/nanosheet feed ratio. Surface oxygen functionalization along GO, GNS, and their nanocomposites influenced the loading, dispersivity, and morphology of nanoparticle agglomerates. PPy/GO nanocomposites yielded an improved nanoagglomerate surface dispersion and loading compared to samples. The PPy-coated substrates offered a greater intrinsic propensity for redox processes, resulting in higher Pt loadings. Additionally, these nanocomposites provided more surface reduction sites compared to bare nanosheets, and the additional sites contributed toward forming smaller, more homogeneously dispersed Pt nanoparticle agglomerates. Bringing together the electrical properties of PPy and physicomechanical traits of carbon nanosheets, it follows to reason that the nanocomposites produced, particularly GO-based nanocomposites, offer promise as a nanoparticle support material for use in catalysis, electrocatalysis, and hydrogen storage.

High performance natural rubber/thermally reduced graphite oxide nanocomposites by latex technology

The latex technology is an innovative alternative for the preparation of composites of natural rubber (NR) and thermally reduced graphite oxide (TRGO). To achieve an improvement of material properties is indispensable to prepare stable suspensions of TRGO. In this work the influence of two surfactants, such as sodium dodecyl sulfate (SDS), as ionic, and Pluronic F 127 as non-ionic surfactant, on the dispersion of TRGO in NR latex and the mechanical and physical properties of the composites were studied. The results showed that the SDS surfactant is ideal for preparing latex NR/TRGO nanocomposite. An optimum dispersion of the nanoparticles in the polymer matrix was achieved in the presence of SDS, as reflected in a considerable improvement of the physical and mechanical properties of the material. Thus, the nanocomposites with 3phr of TRGO exhibited an improvement of nearly 400% in the maximum strength and an electrical percolation threshold with values around 10−6 S/cm, above the static limit.

Ultrasensitive electrochemical biosensor based on graphite oxide, Prussian blue, and PTC-NH2 for the detection of α2,6-sialylated glycans in human serum

α2,6-Sialylated glycans are crucial molecular targets for cancer diagnosis and clinical research. In this work, a novel ultrasensitive electrochemical biosensor was fabricated based on a graphite oxide (GO), Prussian blue (PB), and PTC-NH2 (an ammonolysis product of 3,4,9,10-perylenetetracarboxylic dianhydride) nanocomposite for the selective detection of α2,6-sialylated glycans. To increase the sensitivity of the electrochemical biosensor, gold nanoparticles (GNPs) were immobilized on a GO–PB–PTC-NH2 modified glassy carbon electrode (GCE). Sambucus nigra agglutinins (SNAs), which specifically bind with α2,6-sialylated glycans, were covalently immobilized on GNPs for the sensitive detection of α2,6-sialylated glycans in serum. This proposed method can be applied to human serum, and it worked well over a broad linear range (0.1pgmL−1–500ngmL−1) with detection limits of 0.03pgmL−1. Moreover, recovery of the spiked samples ranged from 100.2% to 105.0%, suggesting that this excellent electrochemical biosensor can be used for the practical detection of α2,6-sialylated glycans.