GO Content Research Articles

Synthesis and characterization of AgBiS2/rGO nanocomposites: Interfacial charge transfer process

AgBiS2-rGO hybrid nano composite has been synthesized by the facile solvothermal technique. The phase formation has been identified by structural analysis which confirmed the formation of AgBiS2-rGO hybrid composite. Raman analysis ensured the presence of AgBiS2, GO and defect state of the graphene. The morphology of composite shown as flakes composed of sphere shaped structure aggregate on the rGO sheets and also well aligned crystallinity with lattice spacing of 0.28 nm of AgBiS2. The embedded AgBiS2 flakes on rGO sheets are highly favourable for fast electron transfer because of its large surface area. The absorption spectrum gradually increased in the near-IR region with the increased content of GO. Tauc plot was used to estimate the optical band gap. The impedance analysis exposed the less charge transfer resistance with the increased GO composition. These results have confirmed the formation of AgBiS2 on rGO and interaction between them.

Ice segregation induced self-assembly of graphene oxide into graphene-based aerogel for enhanced adsorption of heavy metal ions and phenolic compounds in aqueous media

In this study, we reported the synthesis of graphene oxide aerogel (GOA) through ice segregation induced self-assembly of GO sheets. The formation mechanism of GOA was studied via Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller surface area. The GOA with GO concentration of 10 mg/mL was applied as an adsorbent to remove heavy metal ions (Cd2+, Ni2+). The adsorption processes of GOA for Cd2+, Ni2+ fitted well with pseudo-second-order kinetics and Langmuir isotherm models. The maximum adsorption capacities for Cd2+ and Ni2+ were determined to be 108.70 and 91.74 mg/g, respectively. Moreover, the electrostatic attraction was found to be the main interaction between GOA and Cd2+, Ni2+. The adsorption of phenolic compounds (phenol and bisphenol A) was studied to expand the adsorption applications of GOA. In addition, The maximum adsorption capacities for phenol and bisphenol A were determined to be 129.37 and 64.76 mg/g, respectively. Therefore, GOA has the potential to be used as a highly efficient adsorbent for the treatment of heavy metal ions and phenolic compounds from water.

Removal of Cu (II) from aqueous solutions using ZIF-8@GO composites

ZIF-8@GO-X (X ​= ​0, 2.48%, 4.07%, 7.83%, and 20.03%) composites were prepared using GO and ZIF-8. The composites were used to absorb Cu(Ⅱ) from aqueous solutions. With increasing GO content, the adsorption of the ZIF-8@GO-X composites first increased and then decreased. The Cu(Ⅱ) adsorption of ZIF-8@GO-7.83% reaches a maximum among ZIF-8@GO-X composites (X ​= ​0, 2.48%, 4.07%, 7.83%, and 20.03%). The adsorption kinetics, adsorption isotherm, adsorption thermodynamics, and adsorption mechanism of Cu (II) by ZIF-8@GO-7.83% were studied in this paper. The results showed that the adsorption reached equilibrium at 120 ​min, and ZIF-8@GO-7.83% approached equilibrium relatively quickly. When the temperature was 45 ​°C and the Cu(Ⅱ) concentration was 40 ​mg/L, the maximum adsorption capacity of ZIF-8@GO-7.83% for Cu(Ⅱ) reached 482.29 ​mg/g. The equilibrium data and kinetics were well described by Langmuir and pseudo-first-order models, respectively. Final experiments with real factory wastewater (initial Cu(Ⅱ) concentration of 670 ​mg/L) revealed that 0.37 ​g/L ZIF-8@GO-7.83% can efficiently reduce the Cu(Ⅱ) concentration to below 2 ​mg/L.

GO containing PHBHX bone scaffold: GO concentration and in vitro osteointegration

GO containing PHBHX bone scaffold: GO concentration and in vitro osteointegration

Electroless codeposition of GO incorporated silane nanocomposite coating onto AZ91 Mg alloy: Effect of GO content on its morphology, mechanical and corrosion protection properties

The corrosion of Mg alloys is a significant concern in practical applications, and silane-based protective organic coatings are promising to protect the Mg alloys from corrosion. The (3-glycidyloxypropyl) trimethoxysilane/graphene oxide (GPTMS/GO) coating was developed using electroless codeposition technique on AZ91 Mg alloy such that GO sheets were grafted with silanol groups. The coating was prepared by dipping AZ91 Mg alloy in GPTMS/GO solution and then curing at 120 °C. The electrochemical measurement results showed an increased corrosion resistance of AZ91 Mg alloy in 3.5% NaCl solution. The decrease in the corrosion current density value of 0.016 µA cm−2 is attributed to the formation of a passive layer of GO grafted GPTMS on the surface of AZ91 Mg alloy. The enhanced hydrophobicity of 108°, the improved adhesion (5 A) and high hardness (52 HV) were attained due to covalent metallic siloxane bonds (MgOSi) and the laminate structure of GO developed on AZ91 substrate.

Preparation and investigation of optical properties and photocatalytic activity of SnO2/GO thin films

In this paper, SnO2-pure and SnO2/GO thin films with different concentrations of graphene oxide (0, 1, 2, 3 and 4 g/ml) were synthesized using spin coating method. The synthesized thin films were used to study the structural, morphology, chemical, optical and photocatalytic degradation of Methyl Orange (MO) under UV light irradiation by X-ray diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FESEM), Raman spectroscopy, Ultraviolet–visible spectroscopy and UV light respectively. The XRD results of graphene oxide show that the peak is very sharp with high intensity, which indicates a very good crystallinity of the GO structure. The band gape value of SnO2/GO thin films increase by increasing of GO concentration. Under UV light irradiation, the photocatalytic activity of synthesized samples was measured using Methyl Orange dye. The obtained results indicate that by adding graphene oxide concentration, the photocatalytic activity of the tin oxide thin film increases.

Transport properties in spinel ferrite/graphene oxide nanocomposites for electromagnetic shielding

Herein, (Co0.5Ni0.5)Cr0.3Fe1.7O4/graphene oxide nanocomposites were fabricated by ultrasonication technique, using pure spinel ferrite and graphene oxide synthesized by sol-gel method and modified Hummers' method, respectively. The effect of graphene incorporation with ferrite nanoparticles was studied by X-ray diffraction (XRD), electrical and dielectric measurements. XRD analysis revealed the spinel phase for the ferrite sample and confirmed the formation of graphene oxide. The crystallite size was found in the range of 37−43 nm and the porosity increased with the increase in the concentration of graphene oxide in the composites. The DC electrical resistivity of spinel ferrite was found equal to 3.83×109 Ω.cm and it substantially decreased with the increase in the percentage of graphene oxide at room temperature. The real and imaginary part of relative permittivity followed the Maxwell-Wagner type of interfacial polarization. AC conductivity confirmed the conduction by hopping mechanism and increased on increasing the GO content. The coupling of magnetic ferrite with graphene oxide tunes the magneto-electrical properties for potential applications at high frequencies.

Conductive In Situ Reduced Graphene Oxide-Silk Fibroin Bionanocomposites.

This research paper describes the fabrication of bionanocomposites (BNCs) based on silk fibroin (SF) and reduced graphene oxide (rGO). The recorded UV–visible (UV–vis) spectra of the sample confirm the reduction of GO to rGO in SF by showing a plasmon resonance band within the wavelength range of 261–268 nm. The X-ray diffraction (XRD) peak at 11.6° corresponding to the GO intensity decreases with increasing reaction time, resulting in rGO in the SF host matrix. The morphological behavior of the SF–rGO BNCs is scrutinized using scanning electron microscopy (SEM), and the images clearly indicate the existence of rGO within the matrix. The increasing amount of GO in the SF shows broken graphene sheets, which can increase the surface roughness and establish a strong physical contact between the SF and rGO nanosheets. The high-resolution transmission electron microscope (HR-TEM) image of the bionanocomposite showed that the formed rGO encompassments of fewer layers are stacked, each with fewer wrinkles and folding. The Raman spectroscopy confirmed the formation of rGO by showing the increased intensity ratio of D to G band (ID/IG) in the bionanocomposite samples. The rGO effect on the electrical conductivity is measured, and the results show that DC conductivity increases from 1.28 × 10–9 to 82.4 × 10–9 S/cm with an increase in the GO content in the SF biopolymer. The investigations demonstrate loss of the insulation property and improved conducting behavior of the SF biopolymer.

Synergetic effects of dodecylamine-functionalized graphene oxide nanoparticles on antifouling and antibacterial properties of polysulfone ultrafiltration membranes

The potential use of dodecylamine-functionalized graphene oxide (rGO-DDA) nanoparticles as an antifoulant and antibacterial nanofiller was investigated. GO and rGO-DDA were analyzed using Raman spectroscopy, FTIR, SEM, TEM, and TGA that all confirmed the successful functionalization of GO structure. Polysulfone (PSF) ultrafiltration membranes incorporating varied loadings of GO and rGO-DDA were then fabricated via phase inversion approach. All membranes were characterized in terms of chemical structure, morphology, hydrophilicity, porosity and mean pore size. Cross-section SEM images showed the distribution of GO and rGO-DDA between the pores and on the polymer walls. AFM results demonstrated that GO addition increased the roughness of membrane; while with rGO-DDA addition the surface became smoother. Pristine PSF and rGO-DDA based membranes exhibited similar hydrophilicity, while GO-based membranes exhibited higher hydrophilicity as revealed by contact angle measurements. Permeability, separation and antifouling experiments were performed in a cross-flow membrane setup and showed that flux decreases with the increase in GO and rGO-DDA concentration. rGO-DDA membranes showed higher antifouling and antibacterial performance compared to the pristine PSF and GO membranes. Neat PSF exhibited 65.4 % flux recovery ratio (FRR) against BSA that was increased to 86.9 % and 89.1 % with GO-0.1 and rGO-DDA-0.1, respectively. Against HA, FRR was improved from 87.8 % for neat PSF to 95.6 % and 99.3 % with GO-0.1 and rGO-DDA-0.1, respectively. Additionally, rGO-DDA membrane exhibited higher bacteriostatis rate (83.6 %) against H. aquamarina than GO membrane (62.9 %). Moreover, rGO-DDA nanoparticles exhibited excellent dispersibility in several solvents making them promising nanofillers for various membranes with high antifouling and antibacterial performance.

A study on the mechanical properties of graphene oxide/epoxy nanocomposites

The aims of this research are to elucidate the role of graphene oxide on the mechanical properties of epoxy and also to obtain an equation for the modeling of its behavior. Accordingly, graphene oxide/epoxy nanocomposite samples are fabricated using the solution casting method. Tensile, flexural, SEM and FTIR tests are conducted on epoxy and the nanocomposite samples afterwards. The obtained results show that the tensile strength of epoxy improves even at low contents of graphene oxide such that 0.3 wt.% of GO yields an improvement of approximately 11.5%. The flexural strength of epoxy is also enhanced by 5.8% with 0.5 wt.% GO. Then, it decreases due to the agglomeration with increasing the GO content. In order to predict the tensile strength of GO/epoxy nanocomposites, a modified Halpin–Tsai equation is obtained with a new introduced correction factor as K = 39.5 Vf1.135exp(2.9−1644.6 Vf). The obtained equation is in good agreement with the experimental data.

Analysis of Thermal Decomposition Kinetics and Calculation of Activation Energy for Degradation of Polyaniline-Graphene Oxide Composites-Synergistic Reinforcement on Thermal Stability

Thermogravimetric Analysis (TGA) is one of the most commonly used techniques to study the thermal stability of a materials. Thermograms not only give an instant view of the thermal stability but it can also give insights into the degradation kinetics of the material. This study reports on the degradation kinetics of composite materials based on polyaniline and graphene oxide (PANI-GO) synthesized with varying amount of GO. Horwitz & Metzger, Coats & Redfern and Chan et al., methods were employed for calculation of activation energy for degradation, using TGA data. It was observed that their thermal stability and activation energy of degradation are affected by changing the amount of GO during polymerization, indicating PANI and GO synergistically enhance the thermal stability of PANI-GO composites. The highest activation energy value of 29.87 kJ/mol was shown by composite that contain 6 percent GO. Ultraviolet Visible (UV-Vis) spectroscopy, X-Ray Diffraction (XRD) Analysis also support variations in different properties of the composites as a result of changing GO concentration

Preparation of biaxially oriented polyamide 6/polyketone/graphene oxide films with enhanced barrier and mechanical behaviors

AbstractIn this study, biaxially oriented polyamide 6/polyketone/graphene oxide (PA6/PK/GO) films were prepared by melt blending then simultaneously biaxially stretched process, with the aim of obtaining high barrier properties films and improvements in their mechanical properties. The oxygen transmission rate of biaxially oriented PA6/PK/GO film significantly decreased with addition of polyketone and GO. It is surprising that the biaxially oriented process can excellently improve the barrier properties of biaxially oriented PA6/PK/GO film. For example, there was 94.7% OTR reduction of the film containing 20 wt% PK and 0.08 wt% GO compared with PA6 film at a stretching ratio of 3.3 × 3.3. It is due to more tortuous permeation path of oxygen molecule owing to molecular orientation during biaxially stretching, and higher relative crystallinity with addition of GO. The tensile strength of film was remarkablly improved by stretching orientation and increase GO concentration. However, the elongation at break of film was considerably reduced by increase of stretching ratio. Although addition of GO may slightly improve the elongation at break of film at low stretching ratio, there was dramatic decline of elongation at break with increasing the content of GO at a stretching ratio of 3.3 × 3.3.

Microstructure and electrochemical properties of FeNiCoCu medium entropy alloy-graphene oxide composite coatings

FeNiCoCu medium entropy alloy-graphene oxide (MEA-GO) composite coatings were electrodeposited on mild steel substrate and their microstructure and electrochemical properties were investigated as a function of the GO content. The FeNiCoCu MEA coating microstructure consisted of a mixture of Fe, Ni and Co containing body centered cubic (bcc) phase and highly Cu-rich dendritic face centred cubic (fcc) phase. With GO addition, the microstructure changed considerably to one containing highly Fe-rich bcc phase and fcc phase with Ni, Co and Cu elements. Fe-rich phase was present along with GO in the coating microstructure. The MEA coatings uniformity and grains compactness improved with increase in the GO content. Electrochemical properties of the coatings were investigated by open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. It was observed that the corrosion resistance of the MEA coatings increased with increase in their GO content. The enhancement in the corrosion resistance of MEA-GO composite coatings was attributed to the improved coating uniformity, grains compactness, impermeability of GO and formation of relatively stable protective Fe-oxide layer on the coating surface.

Ritual Protostructure of a Work of Art

The article considers the ritual protostructure of a work of art as a text that awakens the process of spiritual initiation (“second birth”) in the recipient’s mind. This is the “inner border” of art, where it shows its derivation from the structure of religious ritual as a symbolic act of overcoming death. Artistry arises where and when our consciousness passes through a point of chaos, through a “break” of being, and then with a new effort again gathers the world into space, fixing this new vision, which has overcome the disintegration, in the strictness of an expressive form. The experience of the “inner”, existential passage through symbolic death can be considered as an analogue of the archaic ritual in the inner world of man. Thanks to this, art in any era effectively fulfilled the existential task of overcoming personal crises. In this aspect, the ultimate ontological categories of human experience — Life, Death, Sacrifice, and Resurrection — fix the basic ontology of a work of art. The general cultural ontology, defined by the dialectic of Space and Chaos, also underlies the structure of artistic reality — this makes it possible to recreate micro- and macrocosms by artistic means. Thanks to this, art in any era effectively fulfilled the existential task of overcoming personal crises. The use of such models for understanding the analysis of the structures of the artwork allows to reconstruct the “inner border” of art — play in this ritual experience of the unity of man with a cosmic mystery of life. The examples of two poems show the “mechanisms” of the ritual meanings of the work of art. Understanding the ritual protostructure of a work can be a valuable basis for using art as a tool for personal development, as a special type of art practice aimed at expanding the existential space of a person. Such art practice is possible only with the ritual understanding of the work as a kind of “existential accelerator”, in which the purely aesthetic, emotional, historical and other aspects of the content of the work go into the context, into the background.

Ultrasound‐assisted synthesis of FeTiO3/GO nanocomposite for photocatalytic degradation of phenol under visible light irradiation

Phenolic compounds are dangerous pollutants in industrial effluents that have caused many human and environmental problems. These compounds are resistant to decomposition conventional biological systems. Photocatalytic treatment is amongst the most efficient technique for phenol removal from aqueous media. In this study, FeTiO3/GO nanocomposite was synthesized through the ultrasound‐assisted method. Structural, morphological, and optical properties of the synthesized nanocomposite were characterized by TEM, XRD, EDS, XPS, BET, TGA, FTIR, and UV–visible techniques. Optimum conditions for phenol photocatalytic degradation were obtained in 3% of GO content, 0.75 g/L nanocomposite dosage, and pH = 8. The degradation efficiency decreased by increasing phenol concentrations and complete mineralization was observed after 240 min of irradiation in optimum conditions. The effect of scavengers indicated that superoxide and hydroxyl radicals had the main role in the photodegradation process. The hindrance effect of inorganic ions was obtained asHCO3- >Cl- > SO42− >NO3-. Our experimental results put forward the FeTiO3/GO nanocomposite as a highly stable catalyst that can successfully remove phenolic compounds from aqueous solutions. Only a 10.8% decrease was observed in phenol degradation efficiency after five cycles, showing high recyclability of the FeTiO3/GO nanocomposite.

Comparative study of embedded functionalised MWCNTs and GO in Ultrafiltration (UF) PVC membrane: interaction mechanisms and performance

ABSTRACT This work presents the development of polyvinyl chloride/functionalised multi-carbon nanotube (PVC/F-MWCNT) membranes and PVC/graphene oxide (PVC/GO) membranes for the improved removal of chemical oxygen demand (COD) from actual petroleum wastewater. Also, this work for the first time presents the proposed interaction mechanism between the contents of PVC/GO and PVC/F-MWCNT membranes as well as the interaction mechanism of each composite membrane with water molecules. The effect of both F-MWCNT and GO content on the characteristics and performance of the PVC/F-MWCNT membrane and PVC/GO membrane were studied. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), contact angle (CA), differential scanning calorimetry (DSC), porosity and tensile strength were used to examine the properties of F-MWCNT, GO, PVC/F-MWCNT and PVC/GO membranes. The composite membranes’ performance was studied by measuring the rejection of chemical oxygen demand (COD) and mass flux. It was found that F-MWCNTs and GO played significant roles in the membranes’ structural morphology. A significant improvement was obtained in the CA, porosity and tensile strength of the membranes by embedding the PVC casting solution with 0.12 wt% of each F-MWCNTand GO. The PVC/F-MWCNTs membrane showed higher performance in term of mass flux and COD rejection that reached 88.9%, which makes using a PVC/F-MWCNTs membrane preferable to remove COD from petroleum wastewater.

A facile cathodic electrophoretic deposition (EPD) of GO nanosheet with an orderly layered nanostructure for development of long-term durability anticorrosive coating

We report the preparation of GO composite coating with an orderly layered nanostructure by cathodic electrophoretic deposition to get long-term durability anticorrosive coatings. The morphological characterization was carried out by scanning electron microscopy, which clearly shows GO nanosheets were orderly stacked. Electrochemical test and corrosion morphology confirmed that the optimized composite coating showed long-term durability exposed in a 3.5 wt.% NaCl solution. The excellent protection of the optimized composite coating is because of the inherent impermeability of GO and the orderly layered nanostructure. First, the orderly layered nanostructure can increase the content of GO and give full play to the inherent impermeability and chemical stability of GO. Second, the orderly stacked GO can reduce the diffusion path of the corrosion medium and retard the degradation of the polymer. Because of the feasibility of EDP technology and the validity of orderly layered nanostructure, this work highlights a workable route for the large-scale preparation of coatings with superior long-term durability, especially for marine engineering materials where resistance to saltwater is of paramount importance.

Nanocomposite powders of hydroxyapatite-graphene oxide for biological applications

The repair of bone fractures is a clinical challenge for patients with impaired healing, such as osteoporosis. Currently, different strategies have been developed to design new biomaterials, enhancing their interactions with biological systems and conducting the cellular behavior in the desired direction to help fracture healing. In the present work, hydroxyapatite-graphene oxide (HA-GO) nanocomposites were produced and the morphological and physicochemical influences of the addition of 0.5 wt%, 1.0 wt% and 1.5 wt% of GO to HA were observed. FEG-SEM and TEM analyses of HA-GO nanocomposites showed HA nanoparticles adhered to the surface of the GO sheets, suggesting an effective method to form nanostructured graphene-based biomaterials. As confirmation, physicochemical analyses by Raman, FTIR and TGA demonstrated a strong affinity between HA and GO, according to the increase of concentration from 0.5 wt% to 1.5 wt% GO in the HA-GO nanocomposites. Also, in order to evaluate the HA-GO nanocomposites behavior under biological microenvironment, in vitro bioactivity and indirect cytotoxicity tests were performed. FEG-SEM analyses confirmed the positive results for the bioactivity properties of HA-GO nanocomposite and indirect cytotoxicity demonstrated that even with a decrease in the hDPSCs viability and proliferation, when increasing to 1.5 wt% of GO concentration, high level of cell viability was exhibited by HA-GO nanocomposites. These biological results suggested the 0.5 wt% HA-GO nanocomposite as a potential bioactive bone graft and a promising biomaterial for bone tissue regeneration, when compared to the pure HA.

Effect of precursor concentration on the performance of UV photodetector using TiO2/reduced graphene oxide (rGO) nanocomposite

This study evaluates the photodetection performance of metal–semiconductor-metal (MSM) ultraviolet photodetector based on TiO2 and TiO2/rGO films deposited on glass substrates. TiO2/rGO thin films with different concentrations of GO (1, 5, 7 and 10 wt%) were deposited on the glass substrates using spray pyrolysis technique (SPT). The TiO2 and TiO2/rGO samples were characterized using Raman spectroscopy, Field Emission Scanning Electron Microscope(FESEM), X-ray diffraction (XRD), and UV spectroscopy (UV) to determine the effect of rGO concentration on the morphology, crystal structure and optical properties of the TiO2/rGO thin films. The successful interface between TiO2 and rGO was confirmed by the broadening characteristic of the XRD peak for anatase TiO2, increasing D and G band intensity ratios (ID/IG) of Raman spectra from 1.05 to 1.9, and decreasing intensity of UV–Vis transmittance spectra as the rGO concentration is increased from 1 to 10 wt%. The decline in the energy bandgap of the thin films from 3.60 to 3.04 eV with the increase in rGO concentration proves the effect of rGO concentration on conductivity. Al metal contacts were sputtered on the thin film samples using RF sputtering to fabricate the MSM photodetector. The photoresponse (R), sensitivity (S%), photodetector gain (G), and recovery times of the photodetector under 375 nm UV illumination (0.37 mW/cm2) and bias voltage of 3 V show that TiO2/rGO thin film prepared via SPT is a promising material for a high quality MSM photodetectors, and confirms the effect of GO concentration on the photodetection performance.

Electrosynthesis of Ni/Al layered double hydroxide and reduced graphene oxide composites for the development of hybrid capacitors

An electrochemical synthesis which has been optimized to produce layered double hydroxides (LDHs) intercalated with carbon nanomaterials is proposed for the first time. It is based on a one-step procedure which contemporaneously allows for the Ni/Al-LDH synthesis, the reduction of graphene oxide (ERGO) and its intercalation inside the structure. The LDH/ERGO composites were thoroughly characterized by a comprehensive multi-techniques approach in order to verify their structure and morphology. The results confirmed that a LDH structure was observed only if the GO concentration was not higher than 0.2 mg/mL. All the characterizations led to propose a theorization of the synthetic and growth mechanisms of the composites. The best performing material was employed as cathode for the development of a hybrid supercapacitor. The device had a discharge specific capacitance of 880 F g−1. The promising results obtained in this work embrace the necessity of development of low environmental impact systems; in fact, the proposed hybrid supercapacitor is binder-free, safe, composed of earth abundant elements and able to work in aqueous electrolyte.