Efficient Reduction Of Graphene Oxide Research Articles

Rapid Yet Efficient Reduction of Graphene Oxide Triggered by Semi-Molten Metals.

Reduced graphene oxide (rGO) has garnered extensive attention as electrodes, sensors, and membranes, necessitating the efficient reduction of graphene oxide (GO) for optimal performance. In this work, a swift reduction of GO that involves bringing GO foam in contact with semi-molten metals like tin (Sn) and lithium (Li) is presented. These findings reveal that the electrical resistance of GO foam is significantly diminished by its interaction with these metals, even in dry air. Taking inspiration from this technique, Sn foil is employed to encase the GO foam, followed by a calcination in 15 vol% H2 /Ar environment at 235°C to fabricate the rGO, which demonstrates a remarkably lower electrical resistivity of 0.42 Ω cm when compared to the chemically reduced GO via hydrazine hydrate (650 Ω cm). The reduction mechanism entails the migration of Sn on GO and its subsequent reaction with oxygen functional groups. SnO/Sn(OH)2 formed from the reaction can be subsequently reversed through reduction by H2 to Sn. Utilizing this rGO as the host material for a sulfur cathode, a lithium-sulfur battery is constructed that displays a specific capacity of 1146 mAh g-1 and maintains a capacity retention of 68.4% after 300 cycles at a rate of 0.2 C.

Gas-driven shearing nanonization of lignin particles for efficient reduction of graphene oxide

Lignin, the second most abundant biopolymer after cellulose, is a promising but still underutilized natural reductant. Nanonization of the bulk lignin into nanoparticles provides a versatile option to enhance its reduction ability by enlarging the specific surface area and making more functional groups exposed to surface. In this work, a novel and simple gas-driven shearing nanonization method with mild operation conditions was explored for green preparation of lignin nanoparticles (LNs). LNs with an average size of ~120 nm were prepared under the working pressure as low as 0.5 MPa. The reduction ability of the as-prepared LNs was investigated by reducing graphene oxide (GO) into graphene. The results indicated that the preparation of LNs could effectively enhance the reduction ability of lignin when compared with the raw lignin. The gas-driven shearing nanonization method offers a green and simple alternative to produce LNs with high-value application prospects.

Facile Green Synthesis of Reduced Graphene Oxide in L-cysteine Solution and its Structural, Morphological, Optical and Thermal Characteristics

The current research reports a cost-effective, efficient ad green reducing agent (L-cysteine) to reduce the graphene oxide (GO) for large-scale reduced graphene oxide (rGO) synthesis. Fabrication of rGO was performed by the reduction of GO using different concentrations from L-cysteine. Synthesis of rGO was noticed by change in color of GO solution from brown to black. For additional confirmation, the structural, morphological, optical and thermal properties of synthesized rGO were analyzed using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray Spectroscopy (EDX) atomic force microscopy (AFM), thermogravimetric analysis (TGA) and ultraviolet-visible spectrophotometer (UV-Vis). The XRD, FTIR and EDS results showed the oxygen-containing groups such as hydroxyl, carbonyl, and epoxy. The UV-Vis spectrum for GO exhibited an absorbance peak at 233 nm which undergoes a red shift of the absorbance peak to 265, 273 and 278 nm due to reduction of GO to rGO using 5, 8 and 10 mg/L of L-cysteine respectively. XRD patterns demonstrated the disappearance of the characteristics peak of GO (11.1) and reinforced this appearance of peak around ~26, indicating the efficient reduction of GO and restoration of graphene sp2 hybridized structure. Furthermore, FTIR spectroscopy showed the gradual disappearance of band at 1745 cm-1 assigned to GO as L-cysteine concentration was increased. The thermal stability of the GO was much lower than those of all the rGO powders where the increased concentration of L-cysteine resulted in enhanced more thermal stability and higher C/O ratio in rGO. The SEM images confirmed the successful structurally exfoliation of two dimensional rGO sheets and showed the folded, curled and flake-like morphology of the graphene nanosheets.

A Novel and Simplest Green Synthesis Method of Reduced Graphene Oxide Using Methanol Extracted Vernonia Amygdalina: Large-Scale Production

The large-scale production of high-quality graphene is the major focus of scientists and engineers recently. However, its massive manufacturing routes from its precursor graphene oxide (GO) are involved in the production of toxic gasses and consist of hazardous explosive steps that severely hurt and threaten ecological balance and human health. Therefore, in this study, we investigated the green, effective, and economical approach for the synthesis of graphene by using Vernonia amygdalina (VA) plant leaf extracts for the effective and efficient reduction of GO. The nonexplosive two-step synthesis of GO in a short period of time in the absence of an ice bath was used in this study. The appropriate solvent for the extraction of VA for the green synthesis of graphene was methanol, and the reducing and capping agent in the plant extract was identified to be terpenoids and polyphenols. The graphene/rGO obtained this way was characterized by UV-VIS, XRD, FTIR, SEM, HR-TEM, and EDAX that confirmed the successful reduction of GO to graphene under the hydrothermal process. The HR-TEM images showed the development of few layers of graphene. The FTIR result also shows the complete reduction of GO. Hence, methanol extracted VA leaves consisted of the most appropriate compounds for reducing and capping agent in the green synthesis and could be the preferred method for the large-scale production of graphene-based materials.

Efficient reduction of graphene oxide to graphene nanosheets using a silica-based ionic liquid: synthesis, characterization and catalytic properties of IMD-Si/FeCl4−@GNS

Ionic liquid-modified graphene nanosheets (IMD-Si/FeCl4−@GNS) have been synthesized as efficient catalysts for the synthesis of (E)-selective thiosemicarbazones.

Advances in Microwave-Assisted Production of Reduced Graphene Oxide.

Efficient reduction of graphene oxide to obtain high-quality graphene nanosheets is desirable for energy storage, catalysis, electronics and environmental remediation. In this brief review, we mainly focus on the microwave-assisted production of reduced graphene oxide in three categories: (1) microwave-assisted chemical reduction of graphene oxide; (2) microwave-assisted thermal reduction of graphene oxide; (3) microwave-assisted simultaneous thermal exfoliation & thermal reduction of graphite oxide. We also summarize common techniques for characterizing reduction efficiency and quality of as-obtained rGO.

A green approach for the reduction of graphene oxide by the ultraviolet/sulfite process

This study highlights a green approach for the reduction of graphene oxide (GO) using the ultraviolet/sulfite advanced reduction process (UV/sulfite process). X-ray photoelectron spectroscopy (XPS) provided a strong evidence on the efficient reduction of GO by increasing the C/O ratio from 2.0 to 4.8, and the successful reduction was also characterized by UV–Vis, XRD and Raman spectrometry. The reduction of GO was attributed to the hydrated electrons generated from both sulfite photolysis (major, contributed by 71.4%) and GO photolysis (minor, contributed by 21.6%) under UV irradiation. The dissolved oxygen in water exhibited inhibitory effect on GO reduction through scavenging of the hydrated electrons. Moreover, the reduction efficiency of GO decreased with the increasing UV wavelength from 254 nm to 365 nm, because of the reduced molar absorptivity of sulfite at higher UV wavelength. By using this green photo-reduction method, high-purity of reduced graphene oxide can be easily obtained by water-rinse, since soluble sulfite are the only by-products. In conclusion, the research outcomes provide mechanistic insights on the GO reduction by the hydrated electron-based advanced reduction processes, which has great potential for the environmental-friendly and cost-effective reduction of GO.

Economic procedure for facile and eco-friendly reduction of graphene oxide by plant extracts; a comparison and property investigation

Hummer’s method which uses concentrated acid and oxidant agents, still is the most productive procedure for production of graphene oxide (GO). However, the reduction of the prepared GO sheets to the reduced graphene oxide (rGO) is the main problem for practical applications. However, the main problem is that prepared GO needs to reduce to graphene for practical applications. Some of the industries where graphene is making an important impact as follows; transport, medicine, electronics, energy, defense and desalination. Conventional methods for reduction of GO, such as thermal annealing or chemical approaches, have been applied frequently. However, they have drawbacks, such as toxic nature of them, their high prices and harmful effects to both environment and human body that make their use undesirable. Here we proposed and tested a green approach including plant extracts for a satisfying reduction of GO to reduced graphene oxide (r-GO) which leads to removing of oxygen containing functional groups. The extracts of Mentha (or Mint) and Tribulus terrestris indicated the moderate antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) test (IC50 = 28 and 33 ppm respectively). After reduction GO by mentioned extracts, the products characterized by XRD, FT-IR, SEM, TEM, Raman and TGA analysis. The obtained results represented that the interaction between GO and Mint extract leads to more efficient reduction of GO in compare to Tribulus terrestris extract. More investigation of Mint extract reduction potential was performed by reducing of GO and Fe3+ ions using Mint extract in the synthesis of rGO/Fe3O4. VSM analysis was a good evidence for suitable reduction of Fe ions and GO, which produced rGO/Fe3O4 nanocomposite with superparamagnetic property.

Reduced Graphene Oxide/Carbon Nanotube Composites as Electrochemical Energy Storage Electrode Applications

We demonstrate an electrochemical reduction method to reduce graphene oxide (GO) to electrochemically reduced graphene oxide (ERGO) with the assistance of carbon nanotubes (CNTs). The faster and more efficient reduction of GO can be achieved after proper addition of CNTs into GO during the reduction process. This nanotube/nanosheet composite was deposited on electrode as active material for electrochemical energy storage applications. It has been found that the specific capacitance of the composite film was strongly affected by the mass ratio of GO/CNTs and the scanning ratio of cyclic voltammetry. The obtained ERGO/CNT composite electrode exhibited a 279.4 F/g-specific capacitance and showed good cycle rate performance with the evidence that the specific capacitance maintained above 90% after 6000 cycles. The synergistic effect between ERGO and CNTs as well as crossing over of CNTs into ERGO is attributed to the high electrochemical performance of composite electrode.

Structural evaluation of reduced graphene oxide in graphene oxide during ion irradiation: X-ray absorption spectroscopy and in-situ sheet resistance studies

We report the structural evolution of reduced graphene oxide (rGO) in graphene oxide (GO) flakes during 1 MeV Si+ ion irradiation. In-situ electrical resistivity measurements facilitate monitoring the sheet resistance with the increase in the fluence. The electrical sheet resistance of the GO flake shows the exponential decay behaviour with the increasing ion fluence. Raman spectra of the GO flake reveal the increase in the ID/IG ratio, indicating restoration of the sp2 network upon irradiation. The C/O ratio estimated from resonant Rutherford backscattering spectrometry analysis directly evidenced the reduction of oxygen moieties upon irradiation. C K–edge X-ray absorption near edge structure spectra reveal the restoration of C=C sp2–hybridized carbon atoms and the removal of oxygen-containing functional groups in the GO flake. STM data reveal the higher conductance in the rGO regime in comparison with the regime, where the oxygen functional groups are present. The experimental investigation demonstrates that the ion irradiation can be employed for efficient reduction of GO with tunable electrical and structural properties.

High Efficient Reduction of Graphene Oxide via Nascent Hydrogen at Room Temperature.

To develop a green and efficient method to synthesize graphene in relative milder conditions is prerequisite for graphene applications. A chemical reducing method has been developed to high efficiently reduce graphene oxide (GO) using Fe2O3 and NH3BH3 as catalyst and reductants, respectively. During the process, environmental and strong reductive nascent hydrogen were generated surrounding the surface of GO sheets by catalyst hydrolysis reaction of NH3BH3 and were used for reduction of GO. The reduction process was studied by ultraviolet absorption spectroscopy, Raman spectroscopy, and Fourier transform infrared spectrum. The structure and morphology of the reduced GO were characterized with scanning electron microscopy and transmission electron microscopy. Compared to metal (Mg/Fe/Zn/Al) particles and acid system which also use nascent hydrogen to reduce GO, this method exhibited higher reduction efficiency (43.6%). Also the reduction was carried out at room temperature condition, which is environmentally friendly. As a supercapacitor electrode, the reversible capacity of reduced graphene oxide was 113.8 F g−1 at 1 A g−1 and the capacitance retention still remained at 90% after 200 cycles. This approach provides a new method to reduce GO with high reduction efficiency by green reductant.

The novel and efficient reduction of graphene oxide using Ocimum sanctum L. leaf extract as an alternative renewable bio-resource

The efficient, rapid, bio-inspired synthesis of reduced graphene oxide (rGO) nanosheets was explored using green leaf extract of Ocimum sanctum L. (Tulsi leaves). This mild biorenewable reducing agent containing eugenol, ascorbic acid, and polyols also acts as a stabilizer for the prepared rGO.

Tea-Carbon Dots-Reduced Graphene Oxide: An Efficient Conducting Coating Material for Fabrication of an E-Textile

The present study reports a facile and green method for reduction of graphene oxide using carbon dots (CDs) derived from “Assam CTC (crush tear curl) Tea”. The efficient reduction of graphene oxide by tea-CDs was monitored using UV–visible spectroscopy. The reduced graphene oxide (rGO) prepared by this method adsorbs some amount of tea-CDs on its surface and forms a very good dispersion in aqueous medium without the use of any other capping or stabilizing agents. Subsequently, the tea-CDs reduced graphene oxide (TCD-rGO) was used for fabrication of a cotton-based conducting fabric with anticipated applicability in different electronic gadgets where high flexibility of the conducting material is required. Coating of cotton with TCD-rGO improved the thermostability of the fabric. The initial degradation temperature for the TCD-rGO coated fabric was found to increase by 30 °C compared to that of the bare cotton fabric. The electrical property of the coated fabric was evaluated. TCD-rGO coated fabric possessed a sheet resistance of 229 ± 20 Ω/sq and electrical conductivity 623 ± 54 S/m, which was comparable to that of the other graphitic conducting textile materials reported so far. The ohmic behavior and the electrical stability of the material was also studied. This particular approach eliminates the use of any toxic chemicals and other high cost synthetic products for fabrication of conducting textiles. Finally, to test the practical viability of the material developed, a stripe from the fabricated conducting fabric was used in a circuit to light up a series of light-emitting diode bulbs.

Self assembly of functionalised graphene nanostructures by one step reduction of graphene oxide using aqueous extract of Artemisia vulgaris

We report self assembly and organisation of graphene sheets to form a macroscopically ordered array of graphene layers using one step reduction of graphene oxide. Aqueous extract of dry leaves of Artemisia vulgaris is used for de-oxygenation of graphene oxide. The reduced graphene oxide samples are investigated for two different reflux times viz. for 6h and 12h. It is found that for an efficient reduction of graphene oxide and for the minimal damage to the crystal structure 6h of reflux is the most favourable. Besides reducing graphene oxide, the phytomolecules also functionalise the graphene layers with electron withdrawing groups by virtue of which three dimensional nanostructures are formed on its surface.

Highly efficient reduction of graphene oxide by sub/supercritical water and their application for thermal interface materials

Heat transfer in the electronics industry has become a critical problem for the progress of miniaturizing device components. As a filler for thermal interface materials (TIMs), graphene has attracted great attention owing to high thermal conductivity and low Kapitza resistance. Therefore, how to obtain high quality and large-scale graphene has become a key issue. In this report, we suggest an approach, which is simple, fast, efficient and eco-friendly, to reduce graphene oxide by sub/supercritical water from 200 to 400 °C. The reduction of graphene oxide is caused by higher temperature and the unique characteristic of water in this temperature range. This hypothesis is verified by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman, thermal gravimetric analysis (TGA) results and comparison experiments. Furthermore, we used the reduced graphene oxide as a filler for graphene-epoxy composites. As a result, the thermal conductivity of the composites significantly increased compared to the pristine epoxy.

LDPE/EVA/graphene nanocomposites with enhanced mechanical and gas permeability properties

In the present work, graphene oxide (GO) and reduced graphene oxide (RGO) were incorporated at low‐density polyethylene (LDPE)/ethylene vinyl acetate (EVA) copolymer blend using solution casting method. Monolayer GO with 1‐nm thickness and good transparency was synthesized using the well‐known Hummers's method. Fourier transform infrared and X‐ray photoelectron spectroscopy data exhibited efficient reduction of GO with almost high C/O ratio of RGO. Scanning electron microscopy showed the well distribution of GO and RGO within LDPE/EVA polymer matrix. The integrating effects of GO and RGO on mechanical and gas permeability of prepared films were examined. Young's modulus of nanocomposites are improved 65% and 92% by adding 7 wt% of GO and RGO, respectively. The tensile measurements showed that maximum tensile strength emerged in 3 wt% of loading for RGO and 5 wt% for GO. The measured oxygen and carbon dioxide permeability represented noticeably the attenuation of gas permeability in composite films compared with pristine LDPE/EVA blend. Copyright © 2015 John Wiley & Sons, Ltd.

Cinnamon supported facile green reduction of graphene oxide, its dye elimination and antioxidant activities

A simple and efficient method of reduction for the preparation of reduced graphene oxide (rGO) from graphene oxide (GO) using Cinnamon (Cinnamomum zeylanicum) extract is reported. The reduction of GO was confirmed by XRD, TEM and UV–visible techniques. The rGO has shown to possess significantly high dye removal property of Malachite green (MG) and Methylene blue (MB) dyes in the absence of UV or Sun light. Further, it showed considerable antioxidant activity against scavenging of 1, 1-Diphenyl-2-picrylhydrazyl (DPPH) free radicals. The study illustrates an environment friendly green method for the efficient reduction of GO.

Spinach assisted green reduction of graphene oxide and its antioxidant and dye absorption properties

Spinach (Spinacia oleracea) leaves mediated efficient green reduction of graphene oxide (GO) was achieved to produce multifunctional reduced graphene oxide (rGO). GO was mixed with spinach juice and refluxed for 30min at 100°C. Powder XRD, TEM and UV–visible techniques demonstrate the formation of well-organized layered rGO. Industrially important carcinogenic Methylene blue (MB) and Malachite green (MG) dyes absorption experiments with rGO were performed under dark condition. Complete removal of MB and MG occurs in spans of 60 and 40min respectively in the presence of 20mg rGO. Potential antioxidant activity was exhibited by the rGO with 50% inhibitory concentration of 1590µg/mL against the scavenging of 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radicals. Environment friendly, economical and facile reduction method is suggested for the efficient reduction of GO.

Laser-Assisted Reduction of Graphene Oxide for Flexible, Large-Area Optoelectronics

This paper reviews recent work on the development and use of a low-temperature, laser-based method for the efficient reduction of graphene oxide (GO) films. The method utilizes a laser beam for the in-situ and nonthermal reduction of solution-processed GO layers onto arbitrary substrates. Compared to other reduction techniques, it is single-step, facile, and can be performed at room temperature in ambient atmosphere without affecting the integrity of the either the graphene lattice or the physical properties of the underling substrate. Using this method, conductive layers of reduced GO with a sheet resistance down to ~700 Ω/sq, are obtained. This is much lower than sheet resistance values reported previously for GO layers reduced by chemical means. As a proof of concept, laser-reduced GO layers were successfully utilized as the transparent anode electrodes in flexible bulk-heterojunction OPVs and as the channel material in field-effect transistors. To the best of our knowledge, this is the only example of an in-situ, postfabrication method for the reduction of GO and its implementation in fully functional opto/electronic devices. The nonthermal nature of the method combined with its simplicity and scalability, makes it very attractive for the manufacturing of future generation large-volume graphene-based opto/electronics.

Ultrafast room-temperature reduction of graphene oxide to graphene with excellent dispersibility by lithium naphthalenide

The reduction of graphene oxide (GO) to graphene is typically carried out under very harsh conditions that require strong reducing agents, elevated temperatures, and long reaction times. Here we introduce a new reducing agent, lithium naphthalenide (LN: ▪), which is distinguished by the very fast (less than 10min) and highly efficient reduction of graphene oxide, even under ambient conditions. In contrast with conventional reducing agents that yield hydrophobic reduced graphene oxide (r-GO), this new reducing agent produces r-GO with enhanced hydrophilicity and a very stable dispersion in water. As an additional advantage, the dispersibility of the resultant r-GO can be easily controlled by varying the washing conditions. This new reducing agent, LN, opens up a practical and economical route to the production of hydrophilic r-GO and broadens the applications of graphene-based materials.