Groups Of Graphene Oxide Research Articles

Facile preparation of graphene aerogel as a thermal insulation material

A simple low temperature and cost-effective hydrothermal method via reduction self-assembly and freeze-drying was fabricated to prepare graphene aerogel (rGO). After the reduction process, most of the oxygen-containing groups in graphene oxide have been removed by ascorbic acid. The surface C/O atomic ratio detected in rGO is about 7.26. The aerogel presents a nanoporous structure. This porous structure could act as a barrier to heat conduction. By heating the graphene aerogel and using infrared thermal imager to detect the temperature, the temperature difference between the top and the bottom of the aerogel reached 80 °C, which showed excellent thermal insulation performance. In addition, by testing the thermal imaging image of graphene aerogel placed on the skin surface, it exhibited an infrared stealth effect. This carbon aerogel may offer potential for the fabrication and application for thermal insulation and infrared stealth material systems.

Electrocatalytic tungsten boride quantum dots anchored reduced graphene oxide as the desolvation promotor for efficient sulfur redox kinetics

Lithium-sulfur (Li-S) batteries boast a multitude of compelling attributes, chief among them being their exceptional energy density and relatively low raw material costs. However, the sluggish redox kinetics of sulfur stemming from the considerable desolvation energy barrier and the notorious shuttle effect of lithium polysulfides, pose significant challenges in the commercialization of Li-S batteries. In this work, ultra-fine WB quantum dots were in-situ and uniformly dispersed on reduced graphene oxide nanosheets (WB-rGO) by mild melting-salt method, in which the abundant oxygen-containing functional groups in graphene oxide effectively prevent the agglomeration of WB. Such ultra-fine WB quantum dot as well as dual-active sites stemming from W and electronics-deficient B, confer the WB-rGO composite with improved electrochemical active surface area for dissociating Li+-solvents molecules and catalyzing polysulfides transformations, thus improving cycling and rate performance of Li-S battery. Hence, the cells with WB-rGO@PP maintained a stable long-term cycling (650 mAh g−1 after 900 cycles at 1 C with an average decay rate of 0.038 % per cycle) and an impressive rate capability (740 mAh g−1 at 4 C). Even at a sulfur loading of 4.7 mg cm−2, the cell performed a high areal capacity of 3.6 mAh cm−2 after 200 cycles.

The Effect of Magnetic Stirring Duration and Ascorbic Acid Concentration on the Yield of Reduced Graphene Oxide Isolated from East Kalimantan Bituminous Coal

East Kalimantan bituminous coal has a carbon composition of 70.24%, indicating a crystal structure of graphite layers. This makes it a viable material for creating reduced graphene oxide (r-GO), which has multiple advantages in various properties and can be employed in numerous technological applications. RGO is obtained by nearly eliminating oxygen functional groups in graphene oxide (GO) through sonication for 3 hours at pH 4. The yield with the lowest value at a 30% concentration of ascorbic acid and 50 minutes of magnetic stirring was selected as optimal. To characterize the resulting product, FTIR was utilized and revealed that O-H (84.21%), C=C (63.04%), and C-O-C (61%) had the highest %T. Technical abbreviations were explained upon first use. Energy-dispersive X-ray (EDX) analysis demonstrated a 90.6% increase in carbon content from 40.159% in GO to 76.554% in r-GO. In parallel, oxygen content decreased from 40,973% in GO to 17.551% in rGO, marking a 57.16% decrease. The morphology of the resulting rGO closely resembled the reference. Additionally, rGO exhibited a C:O ratio of 4.378, surpassing the C:O ratio of GO, which was 1.02. RGO density and pH value were 1.45 g/cm3 and 2, respectively.

Mechanical properties and micromechanics of graphene oxide modified calcareous sand-cement mortar

In the engineering context of island blowing and reclamation, the modification effect of graphene oxide on the mechanical properties of calcareous sand cement mortar is analyzed, and the modification mechanism is elaborated from the microscopic perspective. The experimental results show that graphene oxide promotes the hydration reaction of calcareous sand-cement mortar, and the amount of graphene oxide doping significantly affects the modification effect. The modification effect gradually enhances when the graphene oxide doping amount increases from 0 to 0.06%, and the unconfined compressive strength of the specimens increases up to 36.96%. However, the modification effect decreases when the doping amount is 0.1% compared with that of 0.06%. The results of scanning electron micrographs and energy dispersive spectrometer tests indicate that the addition of graphene oxide accelerates the agglomeration of C-S-H gel produced by the reaction of calcareous sand cement mortar, forming a dense mesh-like structure, which enhances the unconfined compressive strength of the specimens. The oxygen-containing functional groups in graphene oxide are interlinked with the free Ca2+ in the hydration products, eventually producing crystals with the chemical formula (3CaO·Al2O3·CaSO4·12H2O). The generation of crystals leads to the reduction of pores inside the cement mortar and improves the specimen’s compression strength.

Effect of power ultrasound assisted mixing on graphene oxide in cement paste: Dispersion, microstructure and mechanical properties

Dispersed graphene oxide incorporated into cement paste easily reaggregates in an alkaline environment, which is detrimental to the microstructure evolution and mechanical properties. In this study, a novel power ultrasound (PUS) assisted mixing technology was developed for optimizing the dispersion of graphene oxide in cement paste. X-ray computed tomography (X-CT) and Scanning electron microscopy-energy disperse spectroscopy (SEM-EDS) were used to characterize the distribution of graphene oxide. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and mercury intrusion porosimetry (MIP) were adopted to analyze the evolution of the hydration products. The results indicated that PUS-assisted mixing process improved the bonding ability between the Ca2+ and -COO- groups of graphene oxide. Moreover, applying PUS-assisted mixing decreased the average equivalent diameter of graphene oxide agglomerates by 9.9% at 1 day, alongside flexural and compressive strength increments of 26.6% and 3.2%, respectively at 1 day and 22.7% and 12.6%, respectively at 28 days compared with the reference group. The present research can provide a novel approach for the preparation of nanocarbon cement-based materials.

Effect of Four Groups of GO-CF/EP Composites with Ideal Infiltration Structure and Different Layering Ways on Damping Properties.

In this paper, four groups of graphene oxide and carbon fiber hybrid-reinforced resin matrix (GO-CF/EP) composites with different layering ways were prepared by a vacuum infiltration hot pressing system (VIHPS). The damping properties of the specimens with different layering ways were tested by the force hammer method, and the micromorphology of the specimens was photographed by scanning electron microscope. The experimental results showed that the damping properties of GO-CF/EP composites gradually increased with the increase in the number of Y-direction layers. The [XYXYXY]6 has the best damping property, with a damping ratio of 1.187%. The damping ratio is 5.3 times higher than that of [XXXXXX]6 layer mode, and the first-order natural frequency is 77.7 Hz. This is mainly because the stiffness of the X-direction layer is larger than that of the Y-direction layer, and its resistance to deformation is considerable. Therefore, its decay rate is slower. The Y-direction layer has weak resistance to deformation and fast energy attenuation. The increase in the number of Y-direction layers will lead to the overall increase in, and the improvement of, the damping properties of GO-CF/EP composites.

Functional groups in graphene oxide.

Graphene oxide has aroused significant interest for a range of applications owing to their outstanding physico-chemical properties. Specifically, the presence of a large number of reactive chemical moieties such as hydroxyl, carboxyl, epoxide, and sp2 carbon allows these novel materials to be tailored with additional functionalities with the purpose of tuning intrinsic properties. There has been a vivid discussion on the non-covalent modification of GO; however, a comprehensive summary of the chemical functionalization which enables forming a stable particle is still elusive. Hence, in this study, we summarize recently advanced methodologies used for designing the functional GO for their use in specific applications. Together with a brief discussion on the essential characterization techniques, this study will provide fundamental insight into the latest developments in the preparation of covalently modified GO derivatives, thereby leading to their broader utilization in future.

Elektrohemijska svojstva kompozita grafen-oksida i kobalt-ferita dopiranog cinkom i galijumom

This paper presents the electrochemical properties of graphene-oxide composites and nanoparticles of cobalt-ferrite, as well as cobalt-ferrite doped with zinc and gallium. Graphene-oxide (GO) was synthesized by a modified Hummer's method. The magnetic nanoparticles were synthesized by the solvothermal method, after which the oleic acid was exchanged with dihydrocaffeic acid to obtain the hydrophilic material. Composites of graphene-oxide and magnetic nanoparticles were synthesized by the hydrothermal method, where the share of magnetic particles was 5 and 15 wt.% on graphene-oxide. The results of X-ray structural and FTIR analysis confirmed the complete oxidation of graphene layers. SEM and TEM analyzes showed deposition of magnetic nanoparticles on the graphene-oxide layer, without changing the size or shape of the nanoparticles. FTIR analysis of hydrothermally treated graphene oxide and composites showed that there is a partial reduction of epoxy groups, also a hydrogen bond is established between the components of the composite. Cyclic voltammograms show that the composites are stable at polarization rates of 5-400 mV s-1 , and that their capacity is predominantly pseudocapacitive in nature. Pseudocapacitance originates from the oxidoreduction reactions of H+ ions from electrolytes and surface functional groups of graphene-oxide. Based on the cyclic voltammograms, the specific capacities of all composites were calculated and the highest value being shown by the CFO_GO_15% composite, which is 36.86 F g-1 at a polarization rate of 5 mV s-1 .

Reduce and concentrate graphene quantum dot size via scissors: vacancy, pentagon-heptagon and interstitial defects in graphite by gamma rays

Graphene quantum dots (GQDs) with ultrafine particle size and centralized distribution have advantages of small size, narrow size distribution and large specific surface area, which make it be better applied in bioimaging, drug delivery and so on. In our research, we used graphite irradiated by γ-rays to successfully prepare GQDs with ultrafine particle size, narrow size distribution and high quantum yields through solvothermal method. Vacancy defects, pentagon–heptagon defects and interstitial defects were introduced to graphite structure after irradiation, which caused the abundance and concentrated distribution of defects. The defects generated by irradiation could damage the lattice structure of graphite to make it easy for introduction of C–O–C inside graphite sheets. The oxygen-containing functional groups in graphene oxide (GO) increased and centrally distributed after irradiation in graphite, especially for C–O–C group, which were beneficial for cutting of GO and grafting of functional groups in GQDs. Therefore, average size of GQDs was successfully reduced to 1.43 nm and concentrated to 0.6–2.4 nm. After irradiation in graphite, the content of carbonyl and C–N in GQDs had a promotion, which suppressed non-radiative recombination and upgraded the quantum yields to 13.9%.

Ballistic Performance of Ramie Fabric Reinforcing Graphene Oxide-Incorporated Epoxy Matrix Composite.

Graphene oxide (GO) incorporation in natural fiber composites has recently defined a novel class of materials with enhanced properties for applications, including ballistic armors. In the present work, the performance of a 0.5 vol % GO-incorporated epoxy matrix composite reinforced with 30 vol % fabric made of ramie fibers was investigated by stand-alone ballistic tests against the threat of a 0.22 lead projectile. Composite characterization was also performed by Fourier-transform infrared spectroscopy, thermal analysis and X-ray diffraction. Ballistic tests disclosed an absorbed energy of 130 J, which is higher than those reported for other natural fabrics epoxy composite, 74–97 J, as well as plain Kevlar (synthetic aramid fabric), 100 J, with the same thickness. This is attributed to the improved adhesion between the ramie fabric and the composite matrix due to the GO—incorporated epoxy. The onset of thermal degradation above 300 °C indicates a relatively higher working temperature as compared to common natural fiber polymer composites. DSC peaks show a low amount of heat absorbed or release due to glass transition endothermic (113–121 °C) and volatile release exothermic (~132 °C) events. The 1030 cm−1 prominent FTIR band, associated with GO bands between epoxy chains and graphene oxide groups, suggested an effective distribution of GO throughout the composite matrix. As expected, XRD of the 30 vol % ramie fabric-reinforced GO-incorporated epoxy matrix composite confirmed the displacement of the (0 0 1) peak of GO by 8° due to intercalation of epoxy chains into the spacing between GO layers. By improving the adhesion to the ramie fabric and enhancing the thermal stability of the epoxy matrix, as well as by superior absorption energy from projectile penetration, the GO may contribute to the composite effective ballistic performance.

(Invited) Fluorescence and Sensing Applications of Graphene Oxide

This presentation describes the finger-printing fluorescence of functional groups in graphene oxide. In particular, this talk highlights the excitation wavelength-dependent fluorescence emission of graphene oxide. In addition, graphene oxide has been functionalized with aptamers for detection of heavy metals and cancer biomarkers.

Effects of single layer graphene and graphene oxide modification on the properties of phthalocyanine blue pigments

Two copper phthalocyanine blue pigments, C.I. Pigment Blue 15 (B) and C.I. Pigment Blue 15:3 (BGS), were modified with Single layer graphene(G) or graphene oxide(GO). The modified pigments were then characterized using FTIR spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption/desorption isotherms and thermogravimetric analysis. The modifications did not affect the chemical structure of the original pigments but non-covalent interactions between the phthalocyanine pigments and the G (or GO) did form. This greatly reduced aggregation and resulted in more uniform particle size distributions. Modification with both G and GO also resulted in a sharp decreases in the phthalocyanine emission intensities and there were small red-shifts in the absorption peaks. The modification of the pigments also improved their color strengths (116.6–121.4% for B and 106.0–108.8% for BGS), and modification with G improved the color purity. Finally, modification with GO improved the wettability of the original pigments. This is due to the abundant hydroxyl and carboxylic acid groups in graphene oxide.

Fabrication of superelastic and highly conductive graphene aerogels by precisely “unlocking” the oxygenated groups on graphene oxide sheets

Oxygenated groups in graphene oxide (GO) have significant influences on the physicochemical properties of GO. Accurate identification and manipulation of oxygenated groups should be essential for sheets functionalization and assembly, but remains challenging. Herein a novel design of oxygenated groups on GO via a facile alkali-annealing strategy is reported to rationally “unlock” specific groups and increase covalent bonding density on sheets. The structural evolution of epoxy and enriched in hydroxyl are well monitored and verified. Based on the fact that hydroxyl is widely regarded as active sites for cross-linker polyvinyl alcohol, a well interweaved graphene aerogel (GA) with ordered “layer-strut” bracing architectures is successfully fabricated. The constructed GA possesses an ultralow density of 1.73 mg cm−3, exceptional resilience with 85% compressive strength recovery even after 1000 cycles, and high conductivity of 17.1 S m−1, demonstrating the significantly reinforced interplays between adjacent layers. The highest specific conductivity (σ/ρ) of the optimized GA reaches 98.8 S cm2 g−1, which is far superior to conventional GA assembled by GO in as-prepared form and exceeding most graphene-based aerogels reported. This new insight into precise engineering oxygenated structures will provide inspirational ideas towards more elaborate graphene-related architectures and a better overall understanding of GO structure.

Indonesia: Sun Chemical – phthalocyanine blue

Two copper phthalocyanine blue pigments, C.I. Pigment Blue 15 (B) and C.I. Pigment Blue 15:3 (BGS), were modified with Single layer graphene(G) or graphene oxide(GO). The modified pigments were then characterized using FTIR spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption/desorption isotherms and thermogravimetric analysis. The modifications did not affect the chemical structure of the original pigments but non-covalent interactions between the phthalocyanine pigments and the G (or GO) did form. This greatly reduced aggregation and resulted in more uniform particle size distributions. Modification with both G and GO also resulted in a sharp decreases in the phthalocyanine emission intensities and there were small red-shifts in the absorption peaks. The modification of the pigments also improved their color strengths (116.6–121.4% for B and 106.0–108.8% for BGS), and modification with G improved the color purity. Finally, modification with GO improved the wettability of the original pigments. This is due to the abundant hydroxyl and carboxylic acid groups in graphene oxide.

Physical reduction of graphene oxide for supercapacitive charge storage

The oxygen-containing functional groups in graphene oxide (GO) impose considerable limitations in their applications requiring chemical inertness and electrical conductivity such as supercapacitive charge storage. Chemical reduction of GO has been frequently employed; however, processing of large volume of hazardous solvents impose severe environmental concerns. This article demonstrates the optical reduction of freeze dried GO into reduced GO (rGO) by a computer controlled laser engraver as a plug and operate device. The conversion of GO into rGO as a function of laser powers has been monitored by X-ray diffraction, X-ray photon electron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, and field emission scanning microscopy. The rGO thus produced has been evaluated for their charge storage capability in aqueous electrolytes. The best performing laboratory prototype demonstrated one of the best energy density of rGO electrodes in an aqueous electrolyte. The promising properties of the supercapacitors thereby developed as well as cost effectiveness and potential for large scale production engaging laser engraving process, the present work offers numerous potentials for deploying efficient and low cost supercapacitive devices.

Reduced Graphene Oxide Using an Environmentally Friendly Banana Extracts

ABSTRACTOne of the most promising methods to produce graphene in large scale is the use of chemical exfoliation together with chemical reduction to achieve reduced graphene oxide. Replacing conventional reducing agents, such as NaBH4 and hydrazine, with cheap, widely available, safe, environmentally friendly, and easy-to-prepare reducing agents is a key to large-scale commercial production of reduced graphene oxide. In this work, we investigate the effectiveness of utilizing fruit extracts derived from banana peel and juice to reduce graphene oxide. After the reduction, the oxygen-containing functional groups in graphene oxide are effectively removed, and the sp2 hybridized carbon-carbon bonding networks are restored, as evidenced by the characterization using x-ray photoelectron spectroscopy and Raman spectroscopy. Our banana extracts would offer a promising pathway for realizing cheap, safe, and environmentally friendly reducing agents for the upscale production of reduced graphene oxide.

Urtica dioica extract as a facile green reductant of graphene oxide for UV resistant and corrosion protective polyurethane coating fabrication

Reduction of graphene oxide still is one of discussion subjects in scientific communities. The use of toxic chemicals like hydrazine is a well-known procedure for graphene oxide reduction. In this paper, a new ecofriendly, fully scalable, and cheap approach with easy procedure on industrial scale for producing reduced graphene oxide is introduced. The studied method was based on successful reduction of graphene oxide by urtica dioica leaves’ extract in 1 h at 90 °C. Raman spectroscopy evidenced the significant removal of considerable oxygen functional groups in graphene oxide after reduction. Improving corrosion properties by helping the functionalization ability of u. dioica leaves’ extract for superior dispersion in polyurethane coatings was studied as well. Electrochemical impedance spectroscopy measurements along with salt spray exposure test revealed the remarkable role of resultant reduced graphene oxide in protective function of polyurethane coatings before and after accelerated weathering condition. Impedance value in low frequency diagrams reveals more than 99% protection efficiency indicating the great role of u. dioica in barrier property of PU coatings after accelerated weathering condition.

Solvent-induced changes in the graphene oxide absorption spectrum. The case of dimethylsulfoxide/water mixtures

In the present contribution solvation pattern of graphene oxide (GO) in dimethylsulfoxide (DMSO)/H2O mixtures was investigated by means of UV–Vis absorption spectroscopy. It was shown that with increase of the DMSO content, xDMSO, the GO's n–π* transition band, appearing at 307 nm in water, blue-shifts by 34 nm in pure DMSO. Together with an observation of an isosbestic point at 320 nm this finding indicates the changes in the GO's first solvating layer. Analysis of the n–π* transition band transfer energy shows that at xDMSO ≲ 0.55 and xDMSO ≳ 0.55 the GO's groups containing CO fragments are preferentially solvated by H2O and DMSO molecules, respectively. In agreement with the latter, the Wallace-Katz analysis yields two absorbing species in the whole range of xDMSO and one species in water-rich and DMSO-rich regions. Quantum chemical calculations reveals formation of H-bonds between GO's carboxyl groups and both H2O and DMSO molecules. The binding energies of H2O and DMSO molecules with the GO's model basal surfaces point out at possible substitution of water molecules in the GO's first solvation layer by DMSO molecules.

The Variations of Structure and Water Flux Performance of Porous Alumina Supported Graphene Oxide Membrane During Heat Treatment Process

Graphene oxide membrane was fabricated based on a silane-modified Al2O3 ceramic substrate via a parallel dip-coating method. The effect of thermal treatment on the structure and performance of graphene oxide membranes was mainly studied in this paper. The thermal behaviours of graphene oxide powder and membranes were analysed by thermogravimetry (TG) and differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied for micro-morphology analysis. The category and content of chemical bonds were studied by fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS), and the interplanar spacing was investigated by X-ray diffraction (XRD). It was found that the thermal treatment temperature should not exceed 350 °C in order to ensure the integrity of the graphene oxide basic structure. The content of functional groups in graphene oxide was altered along with various temperatures, which led to changes in the contact angle and hydrophilicity. The pure water flux reached 15 L m–2 h –1 under 0.2 MPa pressure when the ceramic substrate was coated with 0.5 mg/mL graphene oxide dispersion and treated at 190 °C. The study indicates that the performance of the graphene oxide/ceramic composite membranes can be optimized by heat treatment.

Role of oxygen vacancies in vanadium oxide and oxygen functional groups in graphene oxide for room temperature CO2 gas sensors

The greenhouse effect is involving global heating and climate change within the world. Carbon dioxide (CO2) is one of the major gas at the origin of this effect, but also the byproduct of human activity. Therefore, monitoring the indoor/outdoor CO2 emission by gas sensors is one of the priorities for environmental preservation. In this paper, the sensing performance of CO2 towards two different O-rich films have been studied; graphene oxide (GO) and vanadium dioxide (VO2). The preparation of GO film has been carried out by spray pyrolysis on fluorine tin oxide (FTO) prepared by the modified Hummers method. While the VO2 film has been sol-gel spin-coated on a glass substrate. Both films have been characterized using XRD, SEM and electrical properties. The CO2 gas sensing mechanism and the role of oxygen vacancies in VO2 are addressing. The oxygen functional groups in GO play a main role in the CO2 gas the sensitivity level and response time. Their gas sensing performances have been investigated based on measuring the response vs recovery time, dynamic response curve analysis and sensitivity. In order to better understand the sensing mechanism, characterization has been done with different gas concentrations. Both GO and VO2 based CO2-sensors are acted as an n-type sensor. Sensing behavior of GO at RT has explained to be mainly mediated by the oxygen functional groups and a wide range of active sites. In the other hand, VO2 contains oxygen vacancies and more defect sites which play a main role in the RT sensing activity and low recovery time.