Graphene Oxide
Graphene oxide
CAS:
Molecular Formula:
Graphene Oxide - Names and Identifiers
| Name | Graphene oxide |
| Synonyms | graphene oxide Graphene oxide |
Graphene Oxide - Physico-chemical Properties
| Density | 0.981 g/mL at 25 °C |
| Appearance | powder or flakes |
| Storage Condition | 2-8°C |
| Refractive Index | n20/D 1.333 |
Graphene Oxide - Risk and Safety
| WGK Germany | 3 |
Graphene Oxide - Introduction
1. Graphene oxide (graphene oxide) is abbreviated as GO, which is the oxide of graphene. Its color is brownish yellow. Common products on the market are powder, flake and solution-like; 2. Graphene oxide is rich in oxygen-containing functional groups, soluble in water, NMP, DMF, ethylene glycol and other solvents; 3. Graphene oxide has the characteristics of high purity and good dispersibility, and can be widely used in the field of catalytic materials, as a catalyst carrier for loading nano-metals, oxides, etc., it can also be used in the field of environmental protection materials, adsorbing heavy metals, dyes and other pollutants, and can also be used in polymer materials, coatings, lithium-ion batteries and super point containers. Graphene oxide technical parameters source leaf number morphology purity thickness carbon content oxygen content sulfur content sheet diameter layer number S28018 gold brown sheet 99.9% 0.33-1.0nm<45>54<10.5-5um single layer S24800 brown yellow powder 98% ~ 1nm<46>50<1.50.2-10um single layer S26783 brown liquid 98% ~ 1nm<46>50<1.50.2-10um single layer
Last Update：2022-10-16 17:40:32
Graphene Oxide - Reference Information
| Overview | graphene is the only existing two-dimensional free state atomic crystal, which is the construction of zero-dimensional fullerene, the basic structural unit of one-dimensional carbon nanotubes and Three-Dimensional Graphite. It has unique physical and chemical properties such as high conductivity, high thermal conductivity, high hardness and high strength, and has broad application prospects in the fields of electronics, information, energy, materials and biomedicine. However, due to the strong van der Waals force, graphene is hydrophobic and easy to agglomerate, which limits its wide application. Graphene Oxide (GO) is a derivative of Graphene, which is a single-layer or multi-layer graphite Oxide formed by exfoliation of graphite Oxide, with a typical quasi-two-dimensional spatial structure, the lamellar contains many oxygen-containing groups, with high specific surface energy, good hydrophilicity and mechanical properties, it has good dispersion stability in water and most polar organic solvents. Compared with graphene, graphene oxide has more excellent performance, which not only has good wettability and surface activity, but also can be intercalated by small molecules or polymers, which can improve the thermal, electrical, mechanical and other comprehensive properties play a very important role. |
| Structure | It is generally believed that graphene oxide has a typical quasi-two-dimensional spatial structure, there are a large number of hydroxyl and carboxyl acid active groups on the sheet, its ion exchange capacity is large (much larger than clay minerals), long chain aliphatic hydrocarbons, transition metal ions, hydrophilic molecules, polymers, and the like are easily inserted between the layers by hydrogen bonds, ionic bonds, covalent bonds, and the like, to form an interlayer compound. The interlaminar spacing of the dried samples was about 0. In the range of 59nm ~ 0.67nm, the equilibrium spacing of GO layer was 45% nm, 75% nm and 1 under the relative humidity of 100%, 0.8 and 0.9, respectively. 15nm, than the recognized original graphite layer spacing 0.34nm, is obviously conducive to the intercalation reaction. The chemical formula was found to be C8O2-X[OH]2X[0 & ltX & lt2] by elemental analysis. CNMR studies show that it is composed of the aromatic region (sp2 carbon atoms) and the aliphatic six-membered ring region (sp3 carbon atoms) formed by the destruction of the lattice by oxidation, the relative size of the two is related to the degree of oxidation. However, due to the different preparation methods, reaction time and operation process, the degree of damage to the carbon layer by oxidation is very different, and the chemical composition and specific structure of the prepared samples are very different, therefore, the determination of its accurate structure is still difficult. |
| preparation method | 1.Brodie method firstly uses fuming HNO3 to treat Natural fine powder graphite. When graphite is oxidized, nitric acid ions invade the graphite sheet layer, and then put into KClO4 for further oxidation, and then put the reactants into a large amount of water for filtration, the filtrate was washed with water until it was nearly neutral, and then dried to obtain graphene oxide. 2.Staudemaier method the graphite powder is treated with a mixture of concentrated sulfuric acid and fuming nitric acid, and KClO4 is also used as the oxidant. The graphene oxide carbon layer obtained by this method is seriously damaged, and a large amount of oxygen-containing functional groups such as carboxyl groups are introduced into the end face of the graphene oxide carbon layer. 3.Hummers method graphite powder and anhydrous sodium nitrate (NaNO3) were added to concentrated sulfuric acid in ice bath, KMnO4 was added under strong stirring, and the residual potassium permanganate and MnO2 were reduced by volume fraction of 3% H2O2, make it colorless. Under the treatment of MnSO4 with hydrogen peroxide, the suspension turned bright yellow. The graphene oxide was obtained by filtration, washing three times, and vacuum dehydration. The lamellar structure has a fold-type structure, and the oxygen content is large, the functional groups are rich, and can be well dispersed in pure water. Fu Ling and others divided the preparation of graphene oxide by Hummers method into three stages: low temperature, medium temperature and high temperature reaction, and pointed out the dosage of graphite and potassium permanganate, the volume of concentrated sulfuric acid, the reaction time at low temperature, the method of adding water in the high temperature reaction is the main process factor affecting the structure and performance of the final product, and the amount of sodium nitrate has little effect on the oxidation degree of the product. This method has a short reaction time, no toxic gas ClO2 is generated, and the safety is high, so it has become a commonly used method for preparing graphene oxide. However, excess permanganate ions can cause potential contamination and thus require treatment with H2O2, water washing and dialysis. 4. Electrochemical method graphite in strong acid (perchloric acid, sulfuric acid or nitric acid), with Hg /Hg2SO4 electrode electrolytic oxidation into water, after drying to obtain graphene oxide. Fig.2 synthesis of graphene oxide |
| Formation of graphene oxide sheets | If graphite is formed by stacking graphene sheets in space, GO is formed by stacking of oxidized graphene. If these graphene oxides are to be dissociated from the GO van der Waals force binding, a certain external force must be applied to them. Common methods include pyrolysis expansion and ultrasonic dispersion. Pyrolysis expansion is the heat treatment of GO, the surface of the sheet of epoxy and hydroxyl decomposition of CO2 and water vapor, when the gas generation rate is greater than its release rate, the interlayer pressure generated may exceed the van der Waals force between the graphene sheets, thereby causing expansion and exfoliation of GO. In this process, the volume of GO can expand tens to hundreds of times, which is the industrial scale application of expanded graphite (EG), the exfoliation of graphene oxide made by this method is not complete (specific surface area ~ 100 m2/g, far less than the theoretical complete exfoliation of 2600/g), and heat treatment can cause the graphene oxide sheet to fold into a worm-like shape, it is also called graphite worm. The principle of ultrasonic dispersion is that the ultrasonic wave radiates between dense and dense phases in the GO suspension, so that the liquid flows and generates tens of thousands of tiny bubbles, which are formed and grown in the negative pressure region where the ultrasonic wave propagates longitudinally, in the process of rapid closure in the positive pressure region, which is called the/cavitation 0 effect, the bubble closure can form an instantaneous high pressure of more than 1000 atmospheres, the continuously generated high pressure is like a series of small "explosions" that continuously impact GO, causing the graphene oxide sheets to rapidly peel off. The exfoliation degree of ultrasonic dispersion is relatively high. Since the graphene oxide does not undergo chemical change in this process, the prepared graphene oxide sheet is an insulator like GO. The pyrolysis expansion will lead to partial deoxidation of graphene oxide sheets, which has the conductivity, and can be directly used as a conductive nano filler without reducing treatment after material molding, however, about 30% of the mass is lost due to the release of CO2. In addition, the surface functional groups of the former are more abundant than that of the latter, which may be more conducive to its complex or self-assembly with the matrix. |
| surface modification | graphene oxide sheets with a large number of hydrophilic acidic functional groups, with Good wettability and surface activity, thus, it can be dispersed in dilute alkaline water and pure water to form a stable colloidal suspension. However, unlike water, the organic solvent cannot penetrate into the voids between the GO sheets and break these hydrogen bonds to peel off. If the density of hydrogen bond donor groups, such as hydroxyl groups, is reduced by chemical functionalization, the strength of interlaminar hydrogen bonds will be weakened, which can reduce the hydrophilicity of GO sheets, this makes it possible to exfoliate it in an organic solvent. At present, the surfactants for surface modification reported in the literature mainly include cationic surfactants, organic isocyanates, long chain aliphatic amines, alkyl amines, amino acids and so on. On the one hand, the surface modification of GO can enhance its lipophilicity, on the other hand, the layer spacing can be increased due to the supporting effect of the intercalation active agent. Both of these two points are beneficial for GO to swell and exfoliate into graphene oxide in an organic solvent to form a nano-scale dispersion system. |
| Chemical reduction | during the preparation of GO, the introduction of oxygen atoms destroys the conjugated structure of the original graphite, the exfoliated graphene oxide loses its conductivity, which limits its application in the synthesis of conductive nanocomposites. Through the chemical or electrochemical reduction method, the graphene network structure bonded to sp2 can be repaired, so that the deoxidation can be achieved by re-graphitization, so that the conductivity of graphene oxide is significantly increased, even comparable to the original graphite. However, the reduction of graphene oxide nanosheets that fall off in water will lead to irreversible aggregation, making it difficult to maintain a single sheet dispersion in the polymer matrix. Commonly used reducing agents are mainly hydrazine water (N2H4 · H2O),NaBH4, and H2 is also useful for the reduction of GO. The surface modification solves the interface problem of the composite, and the chemical principle can restore the conductivity of the graphene nano filler itself. The development of these studies paves the way for the preparation of polymer/graphene conductive composites. |
| composite materials | in the past 10 years, there have been a large number of reports of GO and a variety of Matrix Composites at home and abroad, however, it is not clear whether the graphene oxide can achieve single-piece exfoliation, which can only be referred to as GO/polymer intercalation composite. After 2004, with the stable existence of graphene monolith in ordinary environment confirmed, and the mature application of mechanical exfoliation GO preparation of graphene oxide technology, the synthesis of graphene oxide/polymer nanocomposites was realized in a real sense. Common polymer matrices include polystyrene (PS ), Polyaniline (PAN I), polyacrylamide (PMA), polyvinyl alcohol (PVA) and polycaprolactone (PCL). The polymer direct intercalation method is to insert polymer molecules into GO having a lamellar structure by the action of a solvent or physical action such as mechanical shearing to form a nanocomposite. This is a more traditional method of research. In general, a quantitative amount of a water-soluble polymer solution is put into an alkali dispersion of graphene oxide, and then the resulting aggregates are filtered and dried. In-situ polymerization intercalation is the monomer solution and the GO colloidal dispersion are mixed in advance, so that the monomer molecules are inserted between the GO layers, and then the initiator is added to initiate polymerization, so that the polymerization reaction is carried out between the graphene sheets, the obtained reaction solution can be post-treated to obtain a composite material. In addition, due to the expansion effect of the interlayer polymerization exotherm, the spacing between the GO sheets is expanded, which is conducive to further exfoliation and makes the dispersion of graphene in the matrix more uniform, this method is on the rise. |
| prospect | similar to single-walled carbon nanotubes (SWCNT), graphene has excellent thermal, mechanical and electrical properties. However, polymer molecules are not easy to enter the inner surface of SW CNT, and the huge specific surface area and rich surface functional groups of graphene oxide give it excellent composite properties, after modification and reduction, nano-scale dispersion can be formed in the polymer matrix, so that graphene sheets have greater potential in changing the mechanics, rheology, permeability and degradation stability of the polymer matrix. In addition, because the cost of graphene oxide is low and the raw materials are easily available, it has more competitive advantages than SW CNT. At present, there are patent reports on graphene oxide/polymer composites abroad, and the application fields include hydrogen storage materials for fuel cells in the energy industry, microporous catalyst carriers for synthetic chemical industry, conductive plastics, conductive Coatings and fire retardant materials in the construction industry. In the future, it is estimated that the following three aspects will become a hot spot in the application research of graphene materials:(1) to study the preparation of graphene oxide by industrial mechanical stripping GO, and to provide stable and high quality raw materials for subsequent deep processing. (2) deoxidization and reduction of single exfoliated graphene oxide by chemical reduction or heat treatment to restore its conductive structure by regraphitization, so as to realize the preparation of conductive graphene in an efficient chemical way, it can be used on a large scale in the field of information and electronics. (3) preparation of force, electricity and thermal reinforced composites with graphene as nano filler and self-assembled large area conductive paper materials and application research of these materials. At the same time, the surface of graphene oxide was modified to meet the composite with a variety of substrates. China's graphite mineral resources reserves, quality, production and exports are ranked first in the world. However, the related deep processing technology of graphite is relatively backward. It is urgent to increase research and development to improve the added value of products. Today, the research on GO, graphene oxide and graphene has made a breakthrough, which deserves the attention of the domestic scientific and technological community; relevant departments should invest some funds and strength to increase the intensity of research and development, so that graphene and its composite materials can be applied to various departments of the national economy as soon as possible. |
Last Update：2024-04-09 21:21:28
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Mobile: 18021002903
QQ: 3008007409
Wechat: 18301782025
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