Graphite Oxide Composites Research Articles

Reinforcement effect and mechanism of graphene oxide on mortar with alkali free liquid accelerator

This research mainly investigated the reinforcement effect of graphite oxide (GO) on mortar mixed with alkali free liquid accelerator (AF-LA).The 0.05 % GO and 8.0 % AF-LA were selected as composite additives in cement paste and mortar. Comparative tests showed that the setting time of cement paste was shorter, and the flexural and compressive strength of mortar specimen increased significantly at 1d and 28d. In addition, using XRD combined with TG and SEM analysis, the results showed that GO nanosheets and AF-LA synergistically accelerated cement hydration, especially the hydration of C3S minerals, which resulted in more characteristic portlandite (CH) crystals appearing in the hydration products. Therefore, the above results were the main reasons for the composite of GO and AF-LA to improve the mechanical properties of mortar.

Silver-doped graphite oxide composites used as antimicrobial agents against Staphylococcus aureus, Escherichia coli and Tatumella terrea evaluated by direct TLC bioautography

Silver-doped graphite oxide composites presented mixed Ag and Ag2O crystalline phases accompanied by C/O and ID/IG average ratios of 2.13 and 1.16, associated with a good oxidation degree and high structural disorder or defects in the carbon material, respectively. The low-silver-doped GrO composite showed homogenous silver particle dispersion and a low particle size distribution (96 nm). However, high-silver-doped GrO composites generated materials with high relative crystallinity, silver particle agglomeration, and Ag metal phase promotion. At 3 and 5 mg ml−1 per chromatographic plate, the silver-doped graphite oxide composites were tested by direct TLC bioautography against Staphylococcus aureus, Escherichia coli, and Tatumella terrea microorganisms, where the minimum inhibitory concentration was 3 mg ml−1 per chromatographic plate. At 3.0 mg ml−1 per chromatographic plate, high-silver-doped GrO composites exhibited a 39%, 3.2-fold, and 83% higher retention factor (R f ) compared with the composites with low-silver-doped GrO composites against S. aureus, E. coli, and T. terra microorganisms, respectively. However, both composites showed similar inhibition capacities at 5.0 mg ml−1 per chromatographic plate against the three microorganisms. This behavior may be associated with both composites reaching the threshold limit. In general, the silver acetate amount used in the silver-doped GrO composites influenced the dispersion, crystalline phase promotion, particle size distribution, and the silver particle release capacity, which modified the electrostatic adsorption type between the composites and the bacterial cell walls.

Low-temperature compositing of graphene to nanodiamonds by thermal reduction of graphene oxide and photocatalytic properties

Graphene has become a research hotspot in the field of composites due to its special structure and excellent properties The common preparation methods of graphene matrix composites include solvent (hydrothermal) method, sol-gel method, chemical reduction method, electrochemical deposition method, etc. Nanodiamond/reduced graphite oxide (rGO) composites are directly synthesized by low-temperature heat treatment with nanodiamonds and graphite oxide (GO) powders as raw materials with the aid of GO thermal reduction at 195 °C. The degradation ability of samples to methylene blue (MB) under simulated sunlight was tested. Results indicated that GO was thermally reduced to graphene at low temperature, and rGO well combined with diamond. After the introduction of GO, the lattice of nanodiamond underwent distortion. Diamond and graphene formed a quasi-core–shell structure, and the interface between them was well bonded. The composite had a large specific surface area (Brunauer–Emmett–Teller value of 93.13 m2/g). The addition of GO enhanced the absorbance of the samples and reduced the bandgap of nanodiamond. When the ratio of nanodiamond to GO was 6:1, the sample exhibited excellent sunlight photocatalytic activity, and MB degradation rate reached 99.8 % within 40 min. The reduction reaction of GO at low temperature promoted its rapid combination with nanodiamonds. This method had the outstanding advantages of simple process, environment friendliness, and easy mass production.

Copper Precursor Salt‐Dependent Antimicrobial Activity of Graphite Oxide Composites Against Escherichia coli and Staphylococcus Aureus: Synthesis and Characterization

Graphite oxide (GrO) is doped with Cu(NO3)2 (CuN/GrO) and CuSO4 (CuS/GrO). Face‐centered cubic Cu, monoclinic CuO, and cubic Cu2O mixed crystalline phases are observed. The ID/IG ratio on average is 1.0 for all composites, associated with similar structural disorders and defects. CuN/GrO and CuS/GrO composites increase the C:O ratio by 30% compared to GrO. In Cu(NO3)2‐ and CuSO4‐doped GrO composites, the copper particle dispersion is on the GrO surface and GrO edges, respectively. By agarwell diffusion assay, the CuN/GrO composite presents only inhibition against the Staphylococcus aureus microorganism at 10 mg mL−1 per well. However, using the CuS/GrO composite, the minimum inhibitory concentration is 5 mg mL−1 per well against Escherichia coli and S. aureus microorganisms. In general, the copper precursor salt influences the copper particle localization in the GrO matrix in a different way, modulating the antimicrobial behavior. In this way, it is possible to establish a possible electrostatic adsorption caused by the Cu+ or Cu2+ ions and the negative charges of the bacterial cell membrane, where the adsorption and mass diffusion mechanisms between charged composites and Gram‐positive and Gram‐negative microorganisms are affected by the copper particle arrangement in the composites.

Simultaneous preparation of ZnO/rGO composites through Zn(OH)2 decomposition and graphite oxide reduction and their photocatalytic properties.

ZnO/reduced graphite oxide (rGO) composites were simultaneously prepared by the thermal reduction of graphite oxide (GO) and the decomposition of Zn(OH)2. The samples were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence, and DRS. Results indicate that Zn(OH)2 was heated and decomposed into ZnO at a low temperature (200 ℃), while GO was reduced to graphene. The synthesized ZnO particles were small and loaded on graphene layers. The ZnO/rGO photocatalysts exhibited excellent photocatalytic activity against methylene blue (MB) under simulated sunlight irradiation. The ZnO/50% rGO photocatalyst showed the best MB photodegradation rate of up to 99.7% within 3min. Synchronous reaction provided an efficient, simple, and fast preparation method for ZnO/rGO composites, with an excellent solar photocatalytic degradation ability.

Universitetet i Oslo-67 (UiO-67)/graphite oxide composites with high capacities of toluene: Synthesis strategy and adsorption mechanism insight

In this paper, a simple solvothermal synthesis method was proposed for the preparation of metal organic framework/graphene oxide hybrid nanocomposite (UiO-67/GO). A series of UiO-67/GO composites were prepared by varying the addition forms and amounts of GO, and the optimal synthesis conditions were screened. The composites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission Electron Microscope (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), water contact angles (CA) and thermogravimetric analysis (TGA). The adsorption capacity and the adsorption process of toluene were investigated by dynamic adsorption and adsorption kinetics, respectively. The results indicated that 67/GO-0.5% reached the maximum adsorption capacity (876 mg g−1), which far exceeded the other adsorbents. Kinetic model and the Weber-Morris model correlated satisfactorily to the experimental data. The improved adsorption performance was attributed to GO, which enhanced π-π interaction, promoted defect generation and provided more adsorption sites. Finally, the excellent regeneration performance of the adsorbent was verified by temperature programmed desorption (TPD) and cyclic adsorption–desorption experiments. Moreover, the adsorption mechanism was further revealed. Combined with the related adsorption experiments and the density functional theory (DFT) analysis, the efficient removal of toluene by UiO-67/GO was attributed to the cooperation of defects, π-π interaction and hydrogen bonding.

Improving porosity and water uptake of aluminum metal-organic frameworks (Al-MOFs) as graphite oxide (GO) composites

Composites of the aluminum metal-organic frameworks (Al-MOFs) MIL-100(Al) and CAU-10-H and graphite oxide (GO) have been synthesized (by in-situ MOF formation) with four different GO loadings (from 2 to 16 wt%) for enhanced porosity and water uptake capacity. These composite materials MIL-100(Al)-GO and CAU-10-H-GO were examined by powder X-ray diffraction to show the retention of crystallinity and by scanning electron microscopy to show the retention of the morphology. Nitrogen and water sorption isotherms indicate no loss of mass-weighted surface areas, porosity and uptake capacity. In case of MIL-100(Al)-GO composites, the BET surface areas and porosities from nitrogen sorption data even reveal an increase of 8–12% in surface area with the GO increase from 2 to 9 wt% and an increase of 7–10% in total pore volume with GO loading from 9 to 2 wt%, in comparison to neat MIL-100(Al). In the 2 and 5 wt% CAU-10-H-GO composites, a 4% and 7% increase, respectively, in total pore volume was observed. The water uptake in the MIL-100(Al)-GO composites increased 23% over neat MIL-100(Al) with only 2 wt% GO but dropped again to a small 7% increase upon higher GO loadings up to 16 wt%. To the contrary, in the CAU-10-H-GO composites, the water uptake increases only slightly by 4–6% with 2–8 wt% GO. In particular, the MIL-100(Al)-GO composites showed an increase in the porosities and water uptake due to the synergistic effect from the interaction of MOF and GO with the formation of an additional interface with surface area and void volume. Furthermore, a hydrophilic shift of the water uptake to lower relative pressure p∙p0−1 was observed in the 2, 5, 8, 15 wt% CAU-10-H-GO composites. The MOF-GO composites showed essentially unchanged water sorption data after five water ad- and desorption cycles together with retention of crystallinity, morphology and porosity as verified by powder X-ray diffraction, scanning electron microscopy and by nitrogen sorption isotherm analysis, respectively.

Preparation of silica-decorated graphite oxide and epoxy-modified phenolic resin composites

A multifunctional hybrid curing component (GSD) for epichlorohydrin-modified novolac resin (ENR) was synthesized via grafting poly(amidoamine) (PAMAM)-modified silica nanoparticles (SD) on graphene oxide (GO) using a ring opening reaction. SD and GSD, as two different curing components, were also used in different contents as reinforcing fillers of ENR matrix. Fourier-transform infrared spectroscopy and thermal gravimetric analysis (TGA) results proved amine-decoration of silica nanoparticles and also successful preparation of GSD. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy results were utilized to investigate structure of the SD and GSD multifunctional curing components and also the resulted composites. XRD pattern of GSD shows two peaks at 10.1 and 21.8° which belong to characteristic peaks of GO and silica nanoparticles, respectively, with weak intensities due to grafting of SD on the GO surface. Thermal investigation of the prepared composites by TGA showed that curing ENR with higher contents of GSD was resulted in higher thermal properties. The ENR composite cured with 5 wt% of GSD presented the highest char residue of 20.5% among the other hybrid composites.

Simultaneous determination of ascorbic acid, dopamine, and uric acid with polyaniline/hemin/reduced graphite oxide composite

A novel and highly sensitive electrochemical sensor electrode, polyaniline/hemin/reduced graphite oxide, was synthesized. The electrode was then employed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA), displayed good selectivity as well as excellent sensitivity. It showed low limit of detection of 0.05 µA/µM, 0.02 µA/µM, and 0.07 µA/µM in the simultaneous determination of AA, DA, and UA, respectively. Finally, high reproducibility (relative standard deviation, RSD = 2%, 1.5%, and 1% for AA, DA, and UA) and long storage stability (RSD = 3%, 1.2%, and 2% for AA, DA, and UA) of the electrode was observed.

Preparation and capacitive properties of a free-standing phosphomolybdic acid heteropoly blue modified reduced graphite oxide composite

Polyoxometalates (POMs) have shown great potential for electrochemical energy storage.

Ultrasensitive electrochemical detection of digoxin using graphite oxide and Au-NPs composites

Digoxin is a cardiac glycoside which is widely used as medication in treatment of congestive heart failure and arrhythmias. Unfortunately, digoxin has small therapeutic range (2 ng/mL), excess digoxin concentration in blood plasma can cause intoxication. Therefore, simple and sensitive procedure is required for strict monitoring of digoxin in blood level to minimize the risk of toxicity. In this paper, we report detection of digoxin using Au-NPs and GO composites synthesized with wet chemistry. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy were employed for the confirmation of Au-NPs attachment on the surface of GO. The synthesized Au-NPs-GO composites were deposited on the surface of glassy carbon electrode (GCE) for electrochemical characterization. The electrodes were further incubated with mercaptoacetic acid (MAA) and digoxin antibody (Ab) for the formation of Ab-MAA-Au-NPs-GO modified electrode. MAA conjugation resulted in a 35 % increase in Ipc and 63 % decrease in charge transfer resistance (Rct). Antibody immobilization on MAA modified electrode resulted a sudden drop in both the cathodic peak (anodic peak) currents Ipc(Ipa). Increase in Rct (940 Ω) after Ab functionalization was due to its proteinic nature, which confirmed the formation of Ab-MAA-Au-NPs-GO modified GCE sensors. Work was further extended to probe the charge transfer characteristics in different dilution of digoxin. 17 % (10 %) decrease in Ipc(Ipa) as the digoxin drug was increased from 0.1 ng/mL to 1000 ng/mL. Linear sweep voltammetry (LSV) was also performed at the end for analytic performance of Ab modified sensor for various digoxin drug dilutions. Two linear regressions for current response against digoxin drug dilution were recorded, which confirmed sensitivity of the sensor was governed by interaction between Ab and digoxin drug coordinated by potassium ions at the electroactive sites. The sensitivity was 154.81 μAcm−2 ng-1 for 2-0.1 ng range and 10.71 μAcm−2 ng-1 in the range of 1000−2 ng. The limit of detection (LoD) was 0.19 ng/mL, which suggested that proposed Ab-MAA-Au-NPs-GO modified GCE electrochemical sensor can be successfully applied for future digoxin drug detection applications.

Electrical Properties of Powders of Thermally Reduced Graphite Oxide and Epoxy Composites Based on Them

The effect of annealing thermally reduced graphite oxide powders on their electrical conductivity and density at pressures up to 7 MPa is considered. The specific surface area of ​​the powders is determined at various temperatures of annealing. The complex permittivity of epoxy composites based on these powders used as fillers is measured at frequencies of 1.7, 2.9, and 9.8 GHz. The obtained average value of the dielectric loss tangent of the investigated composites in the specified frequency range exceeded the corresponding average value for epoxy composites based on natural graphite by 5–6 times.

Exfoliation of poly(ethylene glycol)-intercalated graphite oxide composite in water without sonication

A novel method for exfoliating graphite oxide (GrO) was implemented through the mass water absorption of a GrO—poly(ethylene glycol) (GrO—PEG) composite. The GrO—PEG composite was prepared by intercalating PEG into the lamellae of GrO, and the variation of the basal spacing was measured by X-ray diffraction analysis. The yield of graphene was measured with an ultraviolet—visible spectrophotometer, and the properties of graphene oxide (GO) were characterized by atomic force microscopy, transmission electron microscopy (TEM), Raman spectrometry, and Fourier transform infrared spectroscopy. Increasing intercalation time was found to improve the yield of GO, whereas increasing the PEG molecular weight had the opposite effect. The GO sheets produced from the intercalation-absorption-exfoliation process were found to be a four-layer structure. TEM and Raman analyses indicate that the graphitized structure and oxygen groups of GO were preserved during the exfoliation process. Most importantly, the results show that good-quality GO could be prepared via a mild method involving water absorption of a GrO—PEG composite.

Fluorescent detection of cholesterol using p-Sulfonatocalix[4]arene functionalized carbon nanotubes and thermally reduced graphite oxide composites

In the present study, carbon nanotube (CNT), thermally reduced graphite oxide (TRGO), and CNT-TRGO were functionalized with p-sulfonatocalix[4]arene (SC4) and then investigated for fluorescent detection of cholesterol in the presence of rhodamine 6G (R6G). All of the composite samples show effective quenching of R6G fluorescent intensity without cholesterol, but the fluorescence intensity significantly increases with the addition of cholesterol. The results indicate a strong interaction between SC4 composites and cholesterol rather than between the SC4 composites and R6G, increasing R6G fluorescence intensity in the presence of cholesterol due to the release of R6G from the SC4 composites. Formation of the complex, made of the SC4 composite plus the cholesterol, enables the detection of cholesterol in the wide range of cholesterol concentration up to 109 µM. The binding constant between SC4 and cholesterol has been calculated, indicating that the SC4 composites display the maximum binding constant of 1.9 × 104 M−1 with cholesterol.

Facile Synthesis of Flower-Like MnCo2 O4 @PANi-rGO: A High-Performance Anode Material for Lithium-Ion Batteries.

Flower-like MnCo2 O4 was prepared in a self-assembly process and used in the formation of MnCo2 O4 @polyaniline (MnCo2 O4 @PANi) that proceeds by a simple in situ polymerization. The MnCo2 O4 @PANi-reduced graphite oxide (MnCo2 O4 @PANi-rGO) composite was then synthesized by introducing rGO into MnCo2 O4 @PANi. This modification improves the overall electronic conductivity of the MnCo2 O4 @PANi-rGO because of the dual conductive functions of rGO and PANi; it also provides a buffer for the changes in electrode volume during cycling, thus improving the lithium-storage performance of MnCo2 O4 @PANi-rGO. The electrochemical performance of the samples was evaluated by charge/discharge cycling testing, cyclic voltammetry, and electrochemical impedance spectroscopy. MnCo2 O4 @PANi-rGO delivers a discharge capacity of 745 mAh g-1 and a Coulombic efficiency of 100 % after 1050 cycles at a current density of 500 mA g-1 , and is a promising anode material for lithium-ion batteries.

Preparation of reduced graphite oxide loaded with cobalt(II) and nitrogen co-doped carbon polyhedrons from a metal-organic framework (type ZIF-67), and its application to electrochemical determination of metronidazole.

The integration of derivatives ofgranular metal-organic frameworks (MOFs) and an electricallyconductive carbon substrate is an effective way to circumvent the deficiency of powdered pristine MOFs or MOF-derived carbon in practical application. The authors describe the use of graphite oxide (GO) as a substrate for in-situ assembly with the zeolitic imidazole framework ZIF-67. The GO and ZIF-67 composites were converted,via pyrolysis, into reduced graphite oxideloaded withCo/N-co-doped carbon polyhedrons (ZIF-67C@rGO). By using various amounts of GO, a series of ZIF-67C@rGO-x with different fractions of GO were synthesized and utilized as electrode modifiers for the detection of the antibiotic metronidazole (MNZ). The results revealed that the ZIF-67C@rGO-0.06 display best sensing performance. This is likely to be due to its hierarchically open pores, abundant active sites and good electrical conductivity. The sensor, best operated near a working potential around -0.6V (vs. SCE), has a linear response in the 0.5 to 1000μM MNZ concentration range and a 0.05μM detection limit. The sensor was applied to theanalysis of pharmaceutical samples where it showed excellent selectivity, good repeatability and satisfying recoveries. Graphical abstract Schematic representation of preparation and application of ZIF-67C@rGO-x.

Enhancing the catalytic behaviour of HKUST-1 by graphene oxide for phenol oxidation

ABSTRACT The composites of graphite oxide (GrO) and the HKUST-1 framework were synthesized by the typical solvothermal method and applied as heterogeneous catalysts for catalytic wet peroxide oxidation (CWPO) of phenol. XRD, FT-IR, Raman and SEM were conducted to characterize the samples. For catalytic oxidation of 150 mL 100 mg L−1 phenol, the dose of 30 mg (0.2 g L−1) catalysts and 0.46 mL H2O2 were kept constant. The GrO-3/HKUST-1 (3% content of GrO) showed higher catalytic activity than the HKUST-1 framework and other GrO/HKUST-1 composites with 99% phenol conversion and 86% COD removal efficiency were obtained at 50°C after 30 min and 8 h. The effect of temperature (40–80°C) and pH (4–9) on catalytic oxidation of phenol by GrO-3/HKUST-1 was investigated. The results showed that the degradation of phenol was obtained with optimum efficiency at 60°C with complete phenol conversion and 93% COD reduction. Furthermore, the acid and alkali resistance abilities were enhanced to a certain degree by the integration of GrO compared with the parent framework HKUST-1. Three successive runs were conducted in the natural pH (6.8) of 150 mL 100 mg L−1 phenol solution which indicated that the synthesized GrO-3/HKUST-1 composite had satisfactory reusability due to the prevention of carbon deposit and negligible Cu2+ leaching (8 ppm). The GrO/HKUST-1 composite could be a kind of promising heterogeneous catalysts for catalytic degradation of organic compounds. Similar to other catalysts, the catalytic oxidation of phenol also relies on the formation of hydroxyl radicals.

Preparation of Cu nanoparticle‐doped ZIF‐8/RGO composites for effective photodegradation of organic pollutant

Cu nanoparticle‐connected ZIF‐8/reduced graphite oxide (RGO) composite was successfully prepared through a facile hydrothermal reaction using sulfate in this paper. The crossover mechanism of metal nanoparticles loading and RGO decoration to enhance the photocatalytic efficiency of pristine ZIF‐8 was studied. The results showed that the prepared Cu‐S@ZIF‐8/RGO has a strong ability to take advantage of sunlight, indicating an appreciable application prospect. RGO can act as a base to support the whole structure and serve as an electron sink to accept photoexcited electrons, realizing the formation of reactive oxygen species (ROS) and inhibition of electron–hole pair recombination. Cu nanoparticles act as connectors between ZIF‐8 and RGO to transfer electrons and realize the formation of partial ROS on its surface. The doped sulfate radical can promote to extend the utilization of the wavelength range by generating surface states. Cu‐S@ZIF‐8/RGO showed the best photocatalytic activity in simulated sunlight for eliminating rhodamine B and 4‐chlorophenol among all the prepared samples, the structure kept intact even in the presence of different kinds of anions. The crossover study of metal loading and RGO decoration can develop a new way for only UV‐responsive metal–organic frameworks to remove organic contaminants under sunlight irradiation.

Green and facile synthesis of polyaniline/tannic acid/rGO composites for supercapacitor purpose

Polyaniline/reduced graphite oxide (PANI/rGO) composites own promising electrochemical properties. However, the toxicity of commonly used reducers for graphite oxide (GO) and the restacking of rGO greatly obstacle the further development of PANI/rGO composites. To solve these problems, in this study the eco-friendly tannic acid (TA) was used to produce rGO. The results of X-ray diffraction, thermogravimetric analysis, and Raman spectroscopy indicated that TA effectively reduced GO into rGO-TA, and the rGO-TA showed good dispersion stability. Subsequently, PANI/rGO-TA (1:0.1 by weight) composites were synthesized, and their cyclic voltammetric behaviors were studied. The PANI/rGO-TA-24 h composite, in which the rGO was reduced by TA with a sufficient reduction time of 24 h, showed larger specific surface area, a more homogeneous distribution of PANI on the surface of rGO, and higher specific capacitance than the PANI/rGO-HH composite, in which the rGO were produced by using hydrazine hydrate (HH) as reduction agent. Finally, a two-electrode symmetric supercapacitor using PANI/rGO-TA-24 h composite as electrodes was assembled. It exhibited a high energy density of 1.68 W h kg−1 and a high power density of 115 W kg−1 at a current density of 0.5 A g−1.

Degradation of endocrine disruptor, bisphenol-A, on an mixed oxidation state manganese oxide/modified graphite oxide composite: A role of carbonaceous phase

Modified graphite oxide (ΝGO) was used as a support of a manganese oxide of hausmannite type (Mn3O4) nanocatalyst and applied for the degradation of an endocrine disruptor, bisphenol-A (BPA). The prepared nanocomposite/catalyst (NGO-Mn3O4), as well as pure modified graphite oxide and manganese oxide, were characterized by X-ray diffraction, Scanning Electron Microscopy, nitrogen adsorption, X-ray photoelectron spectroscopy, Fourier Transform Infrared Spectroscopy, and potentiometric titration. The maximum removal activity for all the materials was measured at pH = 3. The NGO-Mn3O4 nanocomposite showed the highest removal efficiency of BPA at an ambient temperature without light irradiation and/or the addition of chemicals, which can be attributed to the synergistic effect of the composite formation. The nanocomposite exhibited a high catalytic activity for the degradation/oxidation of BPA, which was dramatically higher than that of the pristine Mn3O4 phase. Modified graphite oxide showed also an enhanced capability for the BPA removal, which was linked to an increased physical adsorption component.