The chemical reduction of graphene oxide is a promising route towards the large scale production of graphene for commercial applications. The current state-of-the-art in graphene oxide reduction, consisting of more than 50 types of reducing agent, will be reviewed from a synthetic chemistry point of view. Emphasis is placed on the techniques, reaction mechanisms and the quality of the produced graphene. The reducing agents are reviewed under two major categories: (i) those which function according to well-supported mechanisms and (ii) those which function according to proposed mechanisms based on knowledge of organic chemistry. This review will serve as a valuable platform to understand the efficiency of these reducing agents for the reduction of graphene oxide.

Chemical reduction of graphene oxide: a synthetic chemistry viewpoint

In this chapter, we discuss a variety of chemical reactions introduced for GO. Among all studies on the chemistry of GO, the largest portion focused on the reduction of GO back to graphene, mainly due to its high relevance to graphene and the gold rush of graphene research over the last decade. However, doping, functionalization and cross-linking of GO are equally, if not more, interesting to chemists, since GO is a giant model compound of polycyclic aromatic hydrocarbon (PAH) oxides. Here, we start with a thorough comparison between various reducing recipes for GO, and follow with some theoretical simulations and predictions on its convertibility toward graphene. In addition to that, we elaborate on extended chemical modifications (covalent and non-covalent), cross-linking, and doping recipes for this macromolecule shown in literature. After all, we intend to show you that GO became a relatively hot research topic, not only due to its relevance to graphene, but also for its high chemical activity and tunability, which enabled the prosperity of its research in various fields led by chemists, materials scientists, biologists, physicists, as well as engineers. It is a perfect paradigm for young researchers as an important subject thrived in interdisciplinary research. After all, when real-life problems come, potential solutions do not impose boundaries between disciplines. All relevant disciplines can offer their input, and contribute together to the final solutions, in which cases communications and collaborations between different researchers need to be encouraged and appreciated.

The Chemistry of Graphene Oxide

Intensive interest in graphene has centered on its unique 2D crystal lattice and remarkable properties that offer unique opportunities to address ever-increasing global energy demands. The past years have witnessed considerable advances in the fabrication of graphene-based materials and significant breakthroughs in advanced energy applications. In this Review, two methodologies for graphene production, namely, the bottom-up growth from hydrocarbon precursors and the top-down exfoliation of graphite (to graphene) and graphite oxide (to graphene oxide followed by reduction) are first summarized. The advantages and disadvantages of these methods regarding their accessibility, scalability, graphene quality, and inherent properties are compared. Particular attention is concentrated on tailored nanostructures, electronic properties, and surface activities of these intriguing materials. The preparation of graphene-based composites containing a wide range of active constituents (e.g., transition metals, metal oxides, and conducting polymers) by in-situ hybridization and ex-situ recombination is also discussed with an emphasis on their microstructures and hybrid architectures. This Review is devoted largely to current developments of graphene and its derivatives and composites in energy conversion (i.e., polymer solar cells, dye-sensitized solar cells, perovskite solar cells, and fuel cells) and energy storage (i.e., lithium-ion batteries and supercapacitors) on the basis of their intrinsic attributes in improving photovoltaic and electrochemical performance. By critically evaluating the relationship between the nanostructures and the device performance, we intend to provide general guidelines for the design of advanced graphene-based materials with structure-to-property tailored toward specific requirements for targeted energy applications. Lastly, the potential issues and the perspective for future research in graphene-based materials for energy applications are also presented. By summarizing the current state-of-the-art as well as the exciting achievements from laboratory research, this Review aims to demonstrate that real industrial applications of graphene-based materials are to be expected in the near future. (1346 references).

Graphene-based materials with tailored nanostructures for energy conversion and storage

Colloidal stability of graphene oxide (GO) is studied in aqueous and organic media accompanied by an improved aggregation model based on Derjaguin-Landau-Verwey- Overbeek (DLVO) theory for ultrathin colloidal flakes. It is found that both magnitude and scaling laws for the van der Waals forces are affected significantly by the two-dimensional (2D) nature of GO. Experimental critical coagulation concentrations (CCC) of GO in monovalent salt solutions concur with DLVO theory prediction. The surface charge density of GO is largely affected by pH. However, theoretical calculations and experimental observations show that the colloidal stability of the 2D colloids is less sensitive to the changes in the surface charge density compared to the classical picture of 3D colloids. The DLVO theory also quantitatively predicts the colloidal stability of reduced GO (rGO). The origin of lower stability of rGO compared to GO is rooted in the higher van der Waals forces among rGO sheets, and particularly, in the removal of...

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Colloidal Stability of Graphene Oxide: Aggregation in Two Dimensions.

The precise control of dimension and mono-dispersibility of graphene quantum dots (GQDs) is still a challenge and new developments in this field are of great interest for scientific community. In this work, we have investigated the feasibility of the production of mono-dispersed spherical GQDs (∼4 nm) based on a treatment solely with ammonia solution as both, reducing and stabilizing agent. The structure, size and shape of the so synthesized GQDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy measurements. The synthesized GQDs show excitation-dependent tunable color emission (violet to green). These GQDs could be potentially used as biomarkers for florescent bioimaging. The GQDs also prove to be excellent sunlight-driven photocatalysts for the photodegradation (45%) of methylene blue (MB) dye. Therefore, these GQDs could find remarkable application in the field of photocatalysis. Electrochemical measurements indicate good rate capability and stability of the GQDs in view of their use as supercapacitor electrode material. The present work not only provides a better explanation of the experimental observations, but also suggests an efficient method for the controllable synthesis of multi-functional GQDs.

Tunable (violet to green) emission by high-yield graphene quantum dots and exploiting its unique properties towards sun-light-driven photocatalysis and supercapacitor electrode materials

A rapid and easy approach for the reduction of graphene oxide by formamidinesulfinic acid

In the title compound, C20H21N3OS2, the piperidinyl ring has a distorted chair conformation. Weak inter­molecular C—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers. The crystal packing exhibits short inter­molecular S⋯S distances of 3.590 (2) A.

https://journals.iucr.org/e/issues/2008/12/00/cv2480/cv2480.pdf

3-Phenyl-2-(piperidin-1-yl)-3,5,6,8-tetra-hydro-4H-thio-pyrano[3',4':2,3]thieno[5,4-d]pyrimidin-4-one.

In the title mol­ecule, C18H17N3O3, the dihedral angle between the mean planes of the furan ring and the quinoline group is 77.4 (2)°. In the crystal structure, inter­molecular N—H⋯N hydrogen bonds link the mol­ecules into centrosymmetric dimers.

/pdf/e-n-furan-2-ylmethyl-ene-4-quinolin-8-yl-oxy-butanohydrazide-3wyvujex8e.pdf

(E)-N′-(Furan-2-ylmethyl­ene)-4-(quinolin-8-yl­oxy)butanohydrazide

Facile Synthesis of Thieno[2,3-d]pyrimidine Derivatives Using Inorganic Base Catalysis

A new and very sensitive and selective chromogenic reagent, 2-methylthiophenyldiazoaminoa-zobenzene (MTDAA), was synthesized and studied in detail for the determination of trace mercury(II) in water samples. The method is based on the color reaction between MTDAA and mercury(II). It was found that mercury(II) reacts with MTDAA in Na2B4O7-NaOH buffer solution (pH = 10.0) to form 1 : 2 red complexes; these show maximum absorption at 520 nm. Beer’s law is obeyed in 0–15 µg of mercury(II) in 25 mL of solution. The apparent molar absorptivity of the complex is 1.33 × 105 L/(mol cm); its limit of quantification, limit of detection, and relative standard deviation are 0.75 ng/mL, 0.27 ng/mL, and 1.0%, respectively, giving better sensitivity. The influence of the reaction variables and the effect of interfering ions are reported; most of the metal ions in water samples can be tolerated in considerable amounts. Only a few ions can interfere with the determination of trace mercury(II), but these can be eliminated by prior extraction. The proposed method is sensitive, simple, and rapid. It has been applied to the determination of trace mercury(II) in water samples with satisfactory results.

https://rd.springer.com/content/pdf/10.1007%2Fs10809-005-0149-z.pdf

Shuang-Ming Meng

Papers

A rapid and easy approach for the reduction of graphene oxide by formamidinesulfinic acid

3-Phenyl-2-(piperidin-1-yl)-3,5,6,8-tetra-hydro-4H-thio-pyrano[3',4':2,3]thieno[5,4-d]pyrimidin-4-one.

(E)-N′-(Furan-2-ylmethylene)-4-(quinolin-8-yloxy)butanohydrazide

Facile Synthesis of Thieno[2,3-d]pyrimidine Derivatives Using Inorganic Base Catalysis

The Color Reaction of Mercury(II) with the New Reagent 2-Methylthiophenyldiazoaminoazobenzene and Its Application

Shuang-Ming Meng

Papers

A rapid and easy approach for the reduction of graphene oxide by formamidinesulfinic acid

3-Phenyl-2-(piperidin-1-yl)-3,5,6,8-tetra-hydro-4H-thio-pyrano[3',4':2,3]thieno[5,4-d]pyrimidin-4-one.

(E)-N′-(Furan-2-ylmethyl­ene)-4-(quinolin-8-yl­oxy)butanohydrazide

Facile Synthesis of Thieno[2,3-d]pyrimidine Derivatives Using Inorganic Base Catalysis

The Color Reaction of Mercury(II) with the New Reagent 2-Methylthiophenyldiazoaminoazobenzene and Its Application

(E)-N′-(Furan-2-ylmethylene)-4-(quinolin-8-yloxy)butanohydrazide