Functional Groups Of Graphene Oxide Research Articles

Radiation synthesis of graphene oxide/composite hydrogels and their ability for potential dye adsorption from wastewater

AbstractA high yield of graphene oxide (GO) was chemically synthesized from graphite powder utilizing adjusted Hummer's method. The contents of acidic functional groups in GO were determined using potentiometric titration. Composite hydrogels dependent on graphene oxide/poly(2‐acrylamido‐2‐methylpropanesulfonic acid)/polyvinyl alcohol (GO/PAMPS/PVA) were synthesized utilizing a 60Co gamma irradiation source at different doses. The synthesized graphene oxide and composite hydrogels were portrayed via X‐ray diffraction, thermogravimetric analysis, and Fourier transform infrared analysis. The morphology of composite hydrogels was characterized by scanning electron microscope. The gel % and swelling % for the prepared hydrogel demonstrated that the swelling % of hydrogel increased with raising AMPS content. Whereas the increment of GO and increasing the irradiation dose lead to a reduction in the swelling %. The influences of pH, GO percentage, initial dye concentration, the adsorbent dosage, contact time, and temperature on the adsorption of basic blue 3 dye were evaluated and the adsorption capacity was 194.6 mg/g at optimum conditions; pH = 6, GO/PAMPS/PVA composite hydrogels with 5 wt% of GO, initial dye concentration = 200 mg/L, adsorbent dose = 0.1 g, solution volume = 50 mL after 360 min at room temperature (25°C). The adsorption of dye onto the GO/PAMPS/PVA composite hydrogels follows Pseudo‐second‐order adsorption kinetics, fits the Freundlich adsorption isotherm model.

Reduction-based engineering of three-dimensional morphology of Ni-rGO nanocomposite

Relying on the reduction of oxygenated functional groups of graphene oxide, the engineering of the morphology of Ni-based reduced graphene oxide (Ni-rGO) nanocomposite was carried out via galvanostatic electrochemical co-deposition by changing the current density in a range of 0.001–0.01 A.cm−2 and loading of 2 g.L−1 of graphene oxide. The morphology has been converted to a porous, rough, and three-dimensional (3D) form by significant incorporation and simultaneous reduction of GO into the structure of Ni-rGO nanocomposite film. Study on 3D morphology by SEM, FT-IR, XRD, and Raman confocal spectroscopy approved simultaneously reduction of oxygenated functional groups. Moreover, we have discussed the impact of rGO incorporated in the structure of Ni-rGO nanocomposite onto the creation of porous 3D-morphology and the enhancement of the electroactive specific surface. This new fascinating mechanism and structure can lead to the enhancement of electroactive components in electrochemical sensors and energy conversion-storage systems.

A Highly Sensitive Non-Enzymatic Urea Sensor Based on Ni(OH)2/Mn3O4/rGO/PANi Nanocomposites Using Screen-Printed Electrodes

Herein, we have developed a highly sensitive non-enzymatic biosensor for the detection of the urea using nickel-manganese oxo/hydroxo metal nanoparticles on reduced graphene oxide, and these nanocomposites were made using the hydrothermal reduction method. Then, the characteristics of these nanocomposites were examined using Fourier transform infrared spectroscopy (FT-IR spectroscopy), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductive coupled plasma (ICP), XRD surface mapping, X-ray Diffraction (XRD) and transmission electron microscopy (TEM). Next, a working electrode modification process was conducted via the electro-polymerization of nanocomposites with aniline on the surface of a screen-printed electrode. We realized that reduction and blocking of all graphene oxide functional groups is important in increasing of sensitivity and prevent protonation of aniline by graphene. Finally, the sensitivity of the modified electrode to urea was evaluated by the cyclic voltammetry method. The results indicate that the sensor works within an acceptable linear range 30 μM to 3.3 mM, (R2 = 0.995, n = 3). Highly sensitivity and the limit of detection are roughly 5139.2 μA mM−1 cm−2 and 16.3 μM, respectively. The sensor demonstrated impressive stability and significant anti-interference properties. Based on these features, it can be concluded that the fabricated sensor is reliable for the non-enzymatic detection of urea.

New insight of tailor-made graphene oxide for the formation of atomic Co-N sites toward hydrogen evolution reaction

The designed synthesis of graphene oxide (GO) for the formation of nitrogen-coordinated atomic metal sites (M−N−C) is crucial for developing efficient M−N−C catalysts. Here, the effect of basal plane oxygen functional groups of GO on the adsorption of cobalt ions and their Co-N transition is investigated by tailoring the oxygen content and composition of oxygen functional groups on the basal plane of GO sheets. The tailor-made GO shows that the specific oxygen functional groups, such as hydroxyl, epoxy, and carbonyl groups, can be efficiently incorporated with formation of defected structures on the basal plane of GO sheets rather than their edge. The adsorption of cobalt ions on the GO sheets and their transition to the Co-N state are systematically investigated by XPS and XAFS analyses. Annealing temperature-controlled experiments reveal that the incorporation of nitrogen around cobalt atoms is facilitated by the increased number of oxygen functional groups on the basal plane rather than those on the edge of GO sheets, which provide energetically favorable environments for Co-N formation. The hydrogen evolution reaction (HER) activities of the resulting cobalt atom-immobilized and annealed GO (Co/GOx-T) catalysts correlate to the degree of Co-N saturation, while also demonstrating excellent HER catalytic durability.

Graphene Oxide Mimics Biological Signaling Cue to Rescue Starving Bacteria

AbstractThere is extensive debate about how 2D nanomaterials such as graphene oxide (GO) affect bacteria. Various effects of GO are proposed, including bacterial growth inhibition or enhancement, killing, and no activity. Herein, we report that GO protects Staphylococcus aureus bacterial cells from death in starvation conditions with up to a 1000‐fold improvement in cell viability. Transcriptomic profiling reveals that bacterial cells in starvation conditions generally shut down metabolic activity, while only cells incubated with GO increase production of specific enzymes involved in the glyoxalase detoxification pathway along with repressed autolysis. The oxygen‐containing functional groups of GO resemble the molecular structure of methylglyoxal, which bacteria produce to adapt to nutrient imbalances and is detoxified by glyoxalase enzymes. The ability of GO to enable bacterial cell survival in starvation conditions and accompanying cellular responses support that bacterial cells perceive GO as a methylglyoxal‐mimicking nanomaterial cue to reshuffle cellular metabolism and defenses.

Photo-anode surface modification using novel graphene oxide integrated with methylammonium lead iodide in organic-inorganic perovskite solar cells

The novel graphene oxide sheet-methylammonium lead iodide (GO-MAPbI3) was used as photoanode surface modification and is used as a photosensitizer for perovskite solar cells. The multi-crystalline presence of GO-MAPbI3-prepared photo-anode surface and surface morphologies were observed by high-resolution electron transmission microscopy and electron scanning microscopy. The selected electron diffraction pattern of GO-MAPbI3 has also been observed in a multi-crystalline nature. GO-MAPbI3 containing the elementary composition was determined using X-ray photoelectron spectroscopy. They consist of Pb 4f5/2 and Pb 4f7/2 and have an energy binding value of 143.9 (eV) and 138.9 (eV). GO-MAPbI3 was a crystalline cubic black color confirmed by an X-ray diffraction pattern. From the Fourier transform infrared spectra, graphene oxide functional groups, methylammonium lead iodide internal hydrogen bonding between the C–N group attached to the C–H group and its corresponding values. The photo-current density-voltage curves are regulated by GO-MAPbI3 coated on a photo-anode giving 8.39% of the power conversion efficiency.

Tuning the oxygen functional groups in graphene oxide nanosheets by optimizing the oxidation time

The most widely used method for the synthesis of graphene in large scale is through the thermal exfoliation and reduction process of graphene oxide (GO). Well know that the physicochemical properties of graphene greatly affected by the oxidation time employed in GO preparation. In this study, GO samples were prepared at different oxidation time through the Hummers' method. The formation of oxygen containing functional groups in GO and their influences onto its’ structure were analyzed and compared. XPS analysis and 13 C NMR revealed the formation of carboxyl groups mainly formed at a longer oxidation time. XRD results obtained indicated that the oxidation time have no effect on the interlayer spacing ( d ) once it reached the optimal extent, however, the graphite stacking order was disrupted due to the insertion of oxygen-containing functional groups. The influence of oxidation time on the stability of GO dispersions was evaluated by zeta potential , which exhibited higher zeta potential and stability at longer oxidation time. This study demonstrates that the integrity and physicochemical properties of GO can be tuned and depend on the type of oxygen-containing functional groups generated at the basal or edge structure, which may foster a range of new applications. • High integrity of GO structure with enriched oxygen functional groups is accomplished within 5-days of oxidation time. • Epoxide and hydroxyl species abundantly formed within 5-days of oxidation time. • Oxidation time is no longer affected the d-spacing of graphitic structure once it reached to the optimal extent. • The oxidation process mainly occurred at the periphery after 5-days oxidation time. • High stability in colloidal system is accomplished in GO with 5 and 7-days oxidation time.

Photoluminescence amplification of cerium incorporated graphene oxide nanoparticles by photoinduced reduction: A mechanistic study highlighting structural orderness

This work demonstrates a strategy to overcome the limitation of weakly luminescent graphene oxide (GO) based materials by using a simple one pot synthesis of enormously luminescent cerium ion incorporated graphene oxide nanoparticles (GO-Ce NPs). Apart from more than 100 fold amplification of photoluminescence intensity compared to graphene oxide, the origin of such enhancement of GO-Ce NPs is investigated by exploring binding interaction between cerium ions and GO NPs and the structural orderness of the GO NPs in presence of cerium. XPS confirms the existence of two oxidation states of cerium in GO-Ce NPs. Experimental observations enable us to conclude a mechanism involving photoinduced reduction of non emissive Ce (IV) to form luminescent Ce (III) accompanied with energy pumping of cerium by photoexcited GO NPs in the structurally ordered GO-Ce nanoparticles. Again, the interaction between the cerium ions and the oxygen containing functional groups of GO leads to decoupling of the functional groups and there by weakens the intensity of luminescence originated from disordered induced defect states which results a non radiative chanel to generate trivalent cerium via single electron transfer from the orbitals of the functional groups to the vacant 4f orbitals of tetravalent cerium.

Graphene oxide/epoxy acrylate nanocomposite production via SLA and importance of graphene oxide surface modification for mechanical properties

PurposeTraditional nanocomposite production methods such as in situ polymerization, melt blending and solvent technique, have some deficits. Some of these are non-homogeneous particle distribution, setup difficulties, time-consuming and costly. On the other hand, three-dimensional printing technology is a quite popular method. Especially, Stereolithography (SLA) printing offers some benefits such as fast printing, easy setup and smooth surface specialties. Furthermore, surface modification of Graphene Oxide (GO) and its effects on polymer nanocomposites are quite important. The purpose of this study is to examine the effect of surface modification of GO nanoparticles on the mechanical properties and morphology of epoxy acrylate (BisGMA/1,6 hexane diol diacrylate) matrix nanocomposites.Design/methodology/approachIn this study, Ultraviolet (UV) curable end groups of synthesized resin were linked to functional groups of graphene oxide, which are synthesized by the Tour method, which is a kind of modified Hummer method. In addition, synthesized GO nanoparticle’s surfaces were modified by 3-(methacryloyloxy) propyl trimethoxysilane. Significant weight percentages of GO were added into the epoxy acrylate resin. Different Wt.% of modified graphene oxide/acrylate resins was used to print test specimens with SLA type three-dimensional printer.FindingsSurface modification has a significant effect on tensile strength for graphene oxide nanoparticles contained composites. In addition, a specific trend was not observed for tensile test results of non-modified graphene oxide. The tendency of impact and hardness test finding were similar for both surfaces modified and non-modified nanoparticles. Finally, the distribution of particles was homogeneous.Originality/valueThis paper is unique because of the inclusion of both surface modifications of graphene oxide nanoparticles and SLA production of nanocomposites with its own production of three-dimensional printer and photocurable polymer resin.

Electrochemical characterization of graphene-type materials obtained by electrochemical exfoliation of graphite

The oxygenated functional groups of graphene oxide (GO) allow for its dispersion in water, biocompatibility and influence the heterogeneous electron transfer rate of redox processes. Therefore, it’s important to determine the experimental conditions leading to GO materials with the desired electrochemical properties for a given application. Herein, few layers electrochemically exfoliated graphene oxide (EGO) flakes were prepared by electrochemical exfoliation of graphite in 0.1 M H2SO4 and the effect of the electric field (applied voltage divided by the distance between the electrodes) was investigated. Raman and XPS analysis evidence two different regimes during the synthesis: slow kinetics of exfoliation at low voltage vs high concentration of OH• radicals at high voltage. The EGO sheets were successfully assembled on a glassy carbon electrode through an aminophenyl-film linker and characterized by cyclic voltammetry in 1 mM [Fe(CN)6]3-/4- to determine electrochemical surface area (ESA) and standard rate constant of electron transfer (k0). The two parameters scale with each other and are sensitive to the type of EGO, confirming the suitability of the platform used in this work to characterize the EGO materials. The highest ESA (0.08 cm2) and the high k0 (0.13 cm−1) were measured with EGO materials obtained at 8–10 V and 6 cm.

Reduced Graphene Oxide-Laminated One-Dimensional TiO2-Bronze Nanowire Composite: An Efficient Photoanode Material for Dye-Sensitized Solar Cells.

A facile one-step hydrothermal method was developed to prepare reduced graphene oxide-laminated TiO2–bronze (TiO2-B) nanowire composites (TNWG), which contain two-dimensional graphene oxide nanosheets and TiO2-B nanowires. In the hydrothermal process, the functional groups of graphene oxide were reduced significantly. Dye-sensitized solar cells (DSSCs) were fabricated using TNWG as the photoanode material. The effects of different reduced graphene oxide contents in TNWG on the energy conversion efficiency of the dye-sensitized solar cells were investigated using J–V and incident photon-to-current conversion efficiency characteristics. DSSCs based on a TNWG hybrid photoanode with a reduced graphene oxide content of 8 wt % demonstrated an overall light-to-electricity conversion efficiency of 4.95%, accompanied by a short-circuit current density of 10.41 mA cm–2, an open-circuit voltage of 0.71 V, and a fill factor of 67%, which were much higher than those of DSSC made with a pure TiO2-B NW-based photoanode. The overall improvement in photovoltaic performance could be associated to the intense visible light absorption and enhanced dye adsorption because of the increased surface area of the composite, together with faster electron transport due to reduced carrier recombination.

Modification of graphene and graphene oxide and their applications in anticorrosive coatings

In this article, the applications and modification methods of graphene-based materials [graphene and graphene oxide (GO)] in an organic anticorrosive coating were reviewed. First, this paper introduces the application of graphene-based materials with barrier property and electrical conductivity in anticorrosive coating and then explains the protection mechanisms, respectively. In addition, this paper puts forward some problems of graphene in the anticorrosive coatings, such as how to solve the dispersion of graphene, how to improve the compatibility between graphene and the polymer matrix, and how to enhance the adhesion between the coating and metal interface. Second, this paper summarizes the reported modification methods of graphene and GO in terms of covalent and noncovalent modification. For covalent modification, the modification methods of different functional groups of GO are summarized, such as modification of epoxy group (–C(O)C–), hydroxyl group (–OH), and carboxyl group (–COOH). As for the noncovalent modification, the modification methods of graphene and GO are summarized from the three aspects of π−π interaction, hydrogen bond interaction, and electrostatic interaction, respectively. Finally, the applications of graphene-based materials in anticorrosive coatings are summarized and prospected.

Nitrogen-modified Graphene Synthesis and Modification of H2S Removal Efficiency Comparison

In this paper, multilayer graphene is used as the raw material, graphene oxide is prepared by Hummers' improved method, and Nitrogen-modified Graphene is prepared by solvothermal method. It uses SEM, XRD, XPS, Ramman to characterize the sample morphology, internal composition, internal structure and element content, analyze its chaos and functional group change trend, and get: graphene to graphene oxide to Nitrogen-modified Graphene, graphene oxide The replacement of C atoms by O atoms increases surface wrinkles and increases defects and confusion. Nitrogen-modified Graphene is reduced due to the oxygen-containing functional groups of graphene oxide, reducing functional groups and reducing interlayer materials, resulting in a clean surface and reduced defects. The layer spacing is reduced. Then through a fixed bed reactor, using graphene, graphene oxide, and Nitrogen-modified Graphene as experimental samples, the adsorption of hydrogen sulfide gas was tested and researched: the original graphene and graphene oxide had similar adsorption capacities for hydrogen sulfide gas. Nitrogen-modified Graphene is about 3 times that of the first two experimental samples.

Correlation Between Ammonia Selectivity and Temperature Dependent Functional Group Tuning of GO

Starting from room temperature (27 °C), graphene oxide (GO) was annealed stepwise at 100 °C, 200 °C and 300 °C and detailed structural characterizations like FTIR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron spectroscopy), XRD (X-ray powder diffraction) and Raman spectroscopy revealed that with increase in temperature, transformation from GO to rGO (reduced graphene oxide) took place and complete conversion was achieved at 300 °C. With increase in temperature, the functional groups like epoxy, ether, carbonyl and carboxyl were gradually reduced and at 300 °C, only the hydroxyl group became dominant. The gas sensing study was carried out using NH3 and alcohols in the concentration range of 125 ppb-700 ppm. It was observed that for lower ppm (5-50 ppm) the GO based sensors offered better selectivity towards NH3, while rGO exhibited better NH3 selectivity at higher concentrations (200-700 ppm). Possibly, presence of hydroxyl group is favorable for NH3 adsorption and therefore NH3 selectivity is better in rGO particularly at high concentrations. On the other hand, at low NH3 concentrations, presence of various types of functional groups in GO gives a resultant selectivity which is better compared to that of rGO.

Unsaturated Zn–N2–O active sites derived from hydroxyl in graphene oxide and zinc atoms in core shell ZIF-8@ZIF-67 nanocomposites enhanced CO2 adsorption capacity

In order to form strengthened active sites for superior CO2 adsorption on core shell [email protected] nanocomposites, graphene oxide (GO) with oxygen-containing functional groups was used as support to synthesize hybrid adsorbents with unsaturated Zn–N2–O active sites. The results of XPS O 1s and FTIR analysis revealed that the Me–O functional group content in the 0.5 wt% graphene oxide (GO)-supported core shell [email protected] nanocomposite (38.9 at.%) was much higher than that in the 0.5 wt% reduced graphene oxide (RGO)-supported nanocomposite (19.4 at.%). This was because hydroxyl functional groups in the GO formed coordination bonds with zinc atoms in core shell [email protected] XPS N 1s spectra indicated that the incorporation of oxygen-containing functional groups in GO resulted in the transition of binding form from Me–N4 to Me–N2. The CO2 adsorption capacity of GO-supported core shell [email protected] gradually decreased from 2.15 to 1.30 mmol/g as GO weight percentage increased from 0.5 to 4 wt%, which was consistent with the decrease in BET surface area from 1378 to 585 m2/g and increase in peak pore diameter from 7.7 to 8.2 Å. Density functional theory (DFT) calculations demonstrated that unsaturated Zn–N2–O active sites in GO-supported core shell [email protected] nanocomposites resulted in a decreased OC⋯Zn interaction distance from 4.65 (Zn–N4 sites in core shell [email protected]) to 3.46 Å and an increased binding energy from 34.02 to 38.87 kJ/mol. Therefore, 0.5 wt% GO-supported core shell [email protected] nanocomposites exhibited the highest CO2 adsorption capacity of 2.15 mmol/g (at 273 K and 1 bar), 1.34 times higher than that of core-shell [email protected]

Acid Properties of GO and Reduced GO as Determined by Microcalorimetry, FTIR, and Kinetics of Cellulose Hydrolysis-Hydrogenolysis

Graphene oxide addresses increasing interests as a solid acid catalyst working in water for carbohydrate conversion. If there is a general agreement to correlate its unique catalytic performances to its ability to adsorb sugars, the origin of its acidity remains controversial. In this article, we study the acid strength of graphene oxide (GO) prepared by modified Hummers method and that of reduced GO by calorimetry of NH3 adsorption and by FTIR of pyridine adsorption. Very strong acid sites are detected on GO by calorimetry, while reduced graphene oxide (reGO) is not very acidic. The FTIR of pyridine adsorption shows the prevailing presence of Br∅nsted acid sites and a unique feature, the presence of pyridine coordinated by hydrogen bonds. This exceptionally strong Br∅nsted acidity is tentatively explained by the presence of graphene domains decorated by hydroxyl, carboxylic, or sulfonated groups within the GO sheet, resulting in a high mobility of the negative charges which makes the proton free and explains its strong acidity. Accordingly, only GO is active and selective for native cellulose hydrolysis, leading to 27% yield in glucose. Finally, we show that sugar alcohols cannot be formed directly from cellulose using GO combined with Pt/re-GO under hydrogen, explained by the reduction of oxygenated functions of GO. The instability of the functional groups of GO in a reducing atmosphere is the weak point of this peculiar solid acid.

Bacterial Isolation by Adsorption on Graphene Oxide from Large Volume Sample.

Graphene oxide (GO) is a well-known two-dimensional nanomaterial with broad applications in various fields. In particular, the functional groups of GO has demonstrated significance in the molecular binding interactions. GO is normally coated on a solid surface as it is difficult to handle due to its nano-scaled size. Therefore, chemical properties of surface-coated GO depend on the morphological structure of GO on the surface and the operating conditions during the coating process. Isolation of bacteria from environmental samples such as river and pond water is important for increasing the analytical sensitivity of sensor devices. The main issue in isolation of bacteria from an environmental sample is adsorption capacity per unit time. However, increasing the velocity of water sample to elevate the process rate induces high shear stress on the surface, such that the bacteria adsorption rate on the surface is reduced. In this study, we investigated the morphological and chemical properties of sonicated GO and GO-coated surface by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The sonicated GO-coated beads were successfully used for concentrating bacteria from a large-volume sample as opposed to the conventional methods. It can be concluded that, GO-coated surfaces are prospective platforms for concentrating bacteria from various samples and play a major role in reducing the concentration time.

Selective Proton Transport for Hydrogen Production Using Graphene Oxide Membranes.

Graphene oxide has shown exceptional properties in terms of water permeability and filtration characteristics. Here the suitability of graphene oxide membranes for the spatial separation of hydronium and hydroxide ions after photocatalytic water splitting is demonstrated. Instead of relying on classical size exclusion by adjusting the membrane laminates' interlayer spacings, nonmodified graphene oxide is used to exploit the presence of its natural functional groups and surface charges for filtration. Despite a significantly larger interlayer spacing inside the membrane compared with the size of the hydrated radii of the ions, highly asymmetric transport behavior and a 6 times higher mobility for hydronium than for hydroxide are observed. DFT simulations reveal that hydroxide ions are more prone to interact and stick to the functional groups of graphene oxide, while diffusion of hydronium ions through the membrane is less impeded and aligns well with the concept of the Grotthuss mechanism.

A Novel Approach to Synthesize Reduced Graphene Oxide (RGO) at Low Thermal Conditions

Reduced graphene oxide (RGO) or graphene as it is commonly referred to is currently the most promising nanomaterial with potential applications. Synthesis of RGO starts with oxidation of graphite to graphene oxide (GO) which is further reduced either by chemical or thermal means. However, chemical reduction of GO to RGO involves the use of toxic chemical reagents which are not environmental friendly. Hence, in this work, low-temperature thermal reduction has been utilized to obtain high-quality RGO from GO effectively at a temperature of only 50 °C. The precursor of RGO which is GO is synthesized by modification of Improved Hummer’s method (Marcano et al. in ACS Nano 4(8):4806–4814, 2010), a non-toxic and non-explosive method of GO production. The highly exothermic reactions in producing GO are controlled by using ice baths with magnetic stirring. The prepared samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, Scanning electron microscopy and Energy-dispersive X-ray spectroscopy. All four characterizations confirm the efficient oxidation and reduction that has taken place to produce GO and RGO-4. (RGO formed on the 7th day of the reduction process.) XRD peak of GO at 10.46° corresponding to (001) plane indicating an interplanar spacing of 0.80 nm confirms the proper oxidation of graphite to GO. However, after thermal reduction at 50 °C the 2θ peak of GO at 10.46° shifts to 2θ = 24.15° with an interplanar spacing of 0.36 nm that confirms the formation of RGO-4 with retention of most of the sp2 structures by proper reduction of the oxygenated functional groups of GO. The GO produced is hydrophilic in nature due to existence of large number of oxygen-containing functional groups as shown in FTIR analysis. Raman results show that after reduction of GO to RGO-4 at 50 °C, the ID/IG ratio decreased significantly from 1.93 of GO to 1.00 of RGO-4 indicating highly reduced defects density in RGO-4.

Synthesis of Graphene Oxide Nanoparticles by Laser Ablation System

In this study, graphene oxide (GO) and reduced graphene oxide were synthesized by pulsed Nd:YAG laser with a fundamental wavelength (1064 nm) focused on the pure graphite target which was immersed in distilled water. Different pulse energies were applied in two cases; with and without magnetic field. The synthesized GO and rGO nanoparticles were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) with and without magnetic field. The data show the presence of a magnetic field which illustrated increasing oxygen functional groups of GO. This caused a change in the morphology of the surface of GO, increasing crystallite size from 12.19 nm to 71.2 nm. The interlayer distance (d-space) was reduced from 0.4 nm to 0.25 nm and the absorption peaks that appeared in the spectrum were reduced and shifted toward smallest wavelengths, while the stretching vibration of the O-H group peak was shifted toward largest wavelengths.