Preparation Of Reduced Graphene Oxide Research Articles

A Simple Preparation Method of Reduced Graphene Oxide‐Incorporated BiVO4 Loaded with CoOx Composites and Application to Z‐Schematic Water Splitting under Visible Light Irradiation

The construction of Z‐scheme systems is an efficient strategy to realize water splitting under visible light irradiation. In particular, various photocatalysts can be employed for Z‐scheme systems when a reduced graphene oxide (RGO) is used as an electron mediator. Herein, a simple 1‐step process for the preparation of RGO‐(CoOx/BiVO4) composites is developed. In the developed preparation method, Co ions are oxidized to CoOx by photogenerated holes in BiVO4 accompanied by simultaneous reduction of GO to RGO by photoexcited electrons. The developed preparation method is simpler than a conventional method that contains loading with CoOx by impregnation and subsequent incorporation of RGO by photocatalytic reduction. Z‐schematic water splitting under visible light irradiation proceeds when RGO‐(CoOx/BiVO4) prepared by the 1‐step process is combined with Pt/(CuGa)0.5ZnS2. Moreover, the developed method is also able to be applied to the preparation of RGO‐(FeOx/BiVO4) composites.

Unlocking the Stability of Reduced Graphene Oxide Nanosheets in Biological Media via Use of Sodium Ascorbate

AbstractGraphene oxide and reduced graphene oxide (RGO) are carbon bidimensional nanomaterials largely exploited in biomedicine. Their unique interactions with eukaryotic and prokaryotic cells are used to obtain precise intracellular delivery, to create device coatings, and to design theranostic materials for both therapeutic and imaging applications, mainly in the cancer research field. It is known, however, that the hydrophobic behavior of RGO limits its stability in biological media. Here, the employment of sodium ascorbate (NaA) as a reducing agent for the preparation of RGO to provide a nanomaterial with remarkable suitability for applications in cell culture media is proposed. It is demonstrated via a combined experimental and theoretical approach that NaA is able to yield a peculiar RGO derivative, exerting a twofold effect, that is, C sp2 network restoration upon epoxide reduction and RGO edge functionalization via H‐bonding, lending RGO a so far unexampled dispersibility in aqueous‐based media. The kinetic stability of the bidimensional layers of RGO obtained from NaA is demonstrated together with its superior biocompatibility for drug delivery, unlocking outstanding potentialities for biological applications.

Green Reduction of Graphene Oxide by Macromolecular CMCS to Prepare Self‐Healing Conductive Hydrogel Wound Dressing with Drug/Photothermal Antibacterial Activity

AbstractThe healing of severe skin injury is a complicated process and the development of hydrogel dressing with antibacterial and stimuli responsive abilities is necessary. Recently, reduced graphene oxide (RGO) has been widely used in hydrogel dressings due to its good conductivity and photothermal effects. However, there still exist some problems in the fabrication of RGO‐modified hydrogels, especially in the green preparation and dispersion process of RGO. In this work, macromolecular carboxymethyl chitosan (CMCS) is chosen as the reducing agent for the green preparation of RGO. Hydrogels with antibacterial and stimulus‐responsive properties are constructed via Schiff base condensation between CMCS and oxidized pectin (OP). Over 95% cell viability is observed, which is critical for medical applications. RGO endows the hydrogels with relatively good conductivity, self‐healing properties, and mechanical strength. The diameters of bacteriostasis circle of the hydrogel for Escherichia coli and Staphylococcus aureus increase by 0.2 and 0.8 cm respectively after exposure to NIR for 5 min, resulting from the photothermal antibacterial properties of the hydrogel provided by RGO. This study provides guidance for the design and application of multifunctional wound dressing.

Controllable thermal treatment of reduced graphene oxide for tunable electromagnetic wave absorption performance

The complex process of reduced graphene oxide (RGO) preparation hindered its merits of lightweight, high surface area, and notable dielectric loss in electromagnetic (EM) wave absorption performance. This work introduced a controllable ethanol-assisted hydrothermal and annealing treatment to simplify the preparation of RGO with improved agglomeration and achieved tunable EM wave absorption performance. Among series of RGO materials fabricated with different annealing temperatures, the optimized RGO achieves a strong reflection loss of −49.9 dB with a thickness of 3.9 mm, and a broad effective absorption bandwidth of 7.65 GHz with a thickness of 3.1 mm based on a 2 wt% filler content in the matrix. The vacancy defect density and C/O ratio of RGO were demonstrated to be correlated to the behavior of conductive loss and polarization relaxation for RGO and the interface reflection of EM wave. This controllable thermal treatment successfully enabled the simple preparation of RGO with reduced agglomeration and tunable EM wave absorption and effectively contributed to fabricating other carbon-based dielectric/magnetic materials as high-efficiency electromagnetic absorbers in future.

Defect-repaired reduced graphene oxide caging silicon nanoparticles for lithium-ion anodes with enhanced reversible capacity and cyclic performance

Combining nanoscale silicon with reduced graphene oxide (RGO) is a transformative approach to assembling high capacity silicon-based anodes for lithium-ion batteries (LIBs). However, preparation of RGO via conventional reduction methods always causes abundant structural defects. The crystalline structure and electronic conductivity of the resultant RGO are seriously damaged. Herein defect-repaired RGO (DRGO) building blocks to support silicon nanoparticles (SiNPs) are prepared, showing enhanced reversible capacity and cyclic performance. Specifically, RGO is engineered to produce a cage-shaped shell, enwrapping SiNPs with reserved interspace. Glucose is used to repair the defects in the graphene oxide (GO) to generate lower-defect RGO. The as-prepared SiNPs embedded in defect-repaired RGO cages (Si@DRGOC) deliver the gravimetric capacity of 2678.4 mA h g−1 at 100 mA g−1 with high coulombic efficiency over 98% as an anode for LIBs. The Si@DRGOC electrode also delivers reasonable rate capacity of 1284.5 mA h g−1 at 2 A g−1, and 2002.7 mA h g−1 as the current density cycling back to 100 mA g−1. This well-engineered structure may provide a promising strategy for fabrication of high-performance LIBs anode materials.

One-pot preparation of reduced graphene oxide from liquid nitrogen tetroxide via redox potential control

Reduced graphene oxide (RGO) was prepared by redox method with liquid nitrogen tetroxide (N2O4) as oxidant source and sodium borohydride (NaBH4) as reducing agent, which could provide an effective way for the treatment and reuse of liquid propellant oxidants. After N2O4 was pretreated with 60 wt% hydrogen peroxide (H2O2), fluorocarbon surfactants (FC-4330), a nonionic polymerized yellow viscous liquid that can significantly reduce the surface tension of the solvent at very low concentrations, was added to the mixture of N2O4 and natural graphite. In order to simplify the synthetic route of graphene, we introduced the redox potential (ORP), a comprehensive index to measure the degree of redox of the reaction system, by which we successfully fused the oxidation stage and reduction stage in the same reaction vessel, in other words, the one-pot method for preparation of RGO has been successfully realized. This method can also be used to accumulate graphene products and determine the yields directly without the necessity to purify and deal with numerous intermediate products. Furthermore, the redox potential of the reaction system was continuously optimized and precisely regulated by automatic sample injection to create the best redox atmosphere for the preparation of RGO, so as to achieve the purpose of improving the yield and quality of graphene. Finally, the optimal process conditions for the preparation of RGO by one-pot method were obtained, that is, the optimal initial ORP range was [1700, 1750] mV at the oxidation stage and [−1200, −1180] mV at the reduction stage. The graphene products can eventually be exfoliated easily between layers with uniform fold distribution, more concentrated particle size distribution and smaller microcrystal size, and simultaneously the stacking number of layers can be stabilized at 1 or 2 layers.

Facile synthesis of graphene via reduction of graphene oxide by artemisinin in ethanol

The preparation of reduced graphene oxide (RGO) by chemical reduction of graphene oxide (GO) usually involves highly toxic reducing agents which are harmful to the environment and human health. In this paper, a mediated facile and relative green approach for the preparation of RGO in ethanol using artemisinin as a reducing agent is reported for the first time. The morphology and de-oxidation efficiency of the obtained RGO were characterized by transmission electron microscope (TEM), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that artemisinin can effectively reduce GO into few-layered RGO with a high carbon to oxygen ratio (11.7). The mechanism for elimination of oxygen-containing functional groups decorated on GO nanosheets by artemisinin was proposed. The important features of relatively environmentally friendly and facile operation procedures endow this approach with great promise in the mass production of RGO and various graphene-based materials, especially for biomaterials.

Synergistic Effect Between Tea Polyphenols and Aluminum Flake on the Reduction of Graphene Oxide.

Chemical reduction of graphene oxide (GO) using nontoxic reductants is a promising and green approach to produce graphene with versatile functionalities in large scale. However, the relatively low reduction extent of the reduced graphene oxide (RGO) is the main hindrance for many applications. In the present work, significantly enhanced reduction of aqueous RGO suspension is achieved by the chemical reduction with combination of tea polyphenols (TPs) and aluminum flake. In comparison with the RGO reduced by TPs only, the defect of the RGO achieved by the combination of TPs and aluminum flake decrease by 6.70%. The sp 2 structure fraction in the RGO increases by 9.67% due to the synergistic effect between TPs and aluminum flake. In addition, a possible mechanism for the synergistic effect between TPs and aluminum flake on the enhanced reduction of RGO is proposed. This approach provides new significant insights on the efficient and environmentally friendly preparation of RGO with much improved quality.

Highly efficient degradation of dyes by reduced graphene oxide–ZnCdS supramolecular photocatalyst under visible light

The assembly of ZnCdS nanoparticles decorated on a 2D platform of reduced graphene oxide (RGO) sheets by a one-pot ionic-liquid-assisted hydrothermal process is reported. The preparation of RGO and the intimate interfacial contact between ZnCdS nanoparticles and the RGO sheets are achieved simultaneously. The structure and composition of the obtained nanocomposites were studied by means of Fourier transform infrared spectrometery, Raman spectrometery, Thermogravimetric analysis, X-ray diffraction, Scanning electronic microscopy and Transmission electron microscopy. The as-prepared RGO-based nanocomposites show excellent photocatalytic activities toward the photo-degradation of organic dyes.

A simple electrochemical approach to fabricate a glucose biosensor based on graphene–glucose oxidase biocomposite

We report a simple electrochemical approach for the immobilization of glucose oxidase (GOx) on reduced graphene oxide (RGO). The immobilization of GOx was achieved in a single step without any cross linking agents or modifiers. A simple solution phase approach was used to prepare exfoliated graphene oxide (GO), followed by electrochemical reduction to get RGO–GOx biocomposite. The direct electrochemistry of GOx was revealed at the RGO–GOx modified glassy carbon electrode (GCE). The electrocatalytic and electroanalytical applications of the proposed film were studied by cyclic voltammetry (CV) and amperometry. It is notable that the glucose determination has been achieved in mediator-free conditions. RGO–GOx film showed very good stability, reproducibility and high selectivity. The developed biosensor exhibits excellent catalytic activity towards glucose over a wide linear range of 0.1–27mM with a sensitivity of 1.85μAmM−1cm−2. The facile and easy electrochemical approach used for the preparation of RGO–GOx may open up new horizons in the production of cost-effective biosensors and biofuel cells.

One-step solid state preparation of reduced graphene oxide

We have developed an easy and scalable chemical reduction method assisted by microwave irradiation for the synthesis of reduced graphene oxide (RGO) nanosheets in solid state. The as-synthesized RGO is characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetry, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. It is revealed that the bulk of the oxygen-containing functional groups are removed from graphene oxide with this one-step reduction method and monolayer RGO sheets are got from its N,N-dimethyl formamide solution. It is found that the ammonium bicarbonate plays a key role in the preparation of RGO. Considering the analysis results, a mechanism for the formation of RGO is proposed. Besides being eco-friendly, when compared to previous chemical techniques, this process has several advantages like low cost, simplicity and short processing times, which may find practical applications in the preparation of graphene-based composites.