I believe Graphene is very familiar to many people. It has honeycomb structure, excellent mechanical properties, electrical properties, and optical properties, etc. In terms of graphene, we might think about graphene oxide. Here in this article, we mainly introduce the preparation method, modification method and current application as well as future prospects of grapheme oxide.
Graphene oxide, as its name implies, is an oxide of graphene. Active oxygen-containing groups are introduced into graphene, and modified graphene flakes are obtained after processing. This process increases the active reaction site and makes graphene oxide more easy to perform surface modification and enriches the functional means, which can effectively improve the compatibility of the modified graphene oxide with solvents and polymers, making it have a wider application in the field of organic and inorganic composite materials.
For the application of powder materials, the premise is that they can be well dispersed in the system used, and the best monodispersion can be achieved, so that the special properties of powder materials can be truly exerted. However, it is very difficult to completely disperse graphene materials in water, because there are almost no hydrophilic groups on the surface of the graphene material. While the hydrophilic groups such as hydroxyl groups and carboxyl groups attached to the graphene oxide can make its dispersibility in water better than graphene.
Introduction to the preparation method
At present, the mainstream method for preparing graphene oxide is the Hummers method. The preparation process can be briefly summarized as:
Introduction to modification method
- Add graphite to strong acid (concentrated sulfuric acid) and strong oxidant (potassium permanganate), and react to obtain graphene oxide;
- Graphene oxide is obtained by magnetic stirring or ultrasonic vibration peeling;
- Graphene oxide is reduced by chemical reduction / thermal reduction to obtain reduced graphene oxide.
Introduction to function
- The functional modification of ATRP (Atom Transfer Radical Polymerization) was performed by using an oxygen-containing functional group fixing initiator on the surface of graphene oxide.
- Fix the initiator on the graphene oxide carbon skeleton to perform ATRP functional modification.
- Functional modification through non-covalent bonding of ATRP polymer and graphene oxide.
- Prepare polymer composites
Graphene oxide can be processed in solution after being functionalized, which is very suitable for preparing high-performance polymer conforming materials.
Of course, in addition to preparing organic materials, it is also possible to prepare inorganic graphene oxide composite materials, such as metals, metal oxides, ceramics and other materials loaded on graphene oxide to make multifunctional materials. For example, the effect of copper / graphene oxide on the catalytic oxidation effect with MB.
The large surface area of graphene oxide can be used as a drug carrier. Grafting drug molecules to the active groups of graphene oxide, can produce functional graphene with good water solubility and biocompatibility, and can also attach molecules with other functions on to make graphene with various functions, such as purifying the environment and adsorbing toxic and harmful substances in water, which greatly enriches the application of graphene.
Graphene oxide, like graphene, also has good anticorrosive properties. The difference is that graphene oxide has more active sites, so it is easier to modify and can be well dispersed in coatings. Its anti-corrosion mechanism is as follows:
(1). Layer by layer stack of graphene oxide. Although graphene is a two-dimensional sheet structure, after layer-by-layer superposition and effective uniform dispersion, a three-dimensional structure can be formed on the product surface. Projection on the product surface will obtain a filling plane to block oxygen in the environment. And the role of water, so as to achieve the purpose of preservation.
(2). Graphene oxide has good stability. Its chemical properties are stable, and it can remain stable and unaffected under high temperature, corrosion, and high oxygen environments. From its preparation method, we can also see that its chemical properties are stable enough to resist corrosion in nature.
(3). Good conductivity. Reduced graphene oxide has excellent proton / electronic conductivity and extremely low electrical conductivity, unblocks the cathodic protection pathway in anticorrosive coatings, improves the utilization of zinc powder, and thereby improves the anticorrosive performance.
First of all, the conductivity of graphene itself is very good. If graphene is functionalized (oxidized), the conjugated network will be damaged, which will cause graphene oxide to have certain insulation properties. However, after reduction treatment, reduced graphene oxide that is less conductive than the original graphene can be obtained. Most of the conductive properties are lost, but the functionalized graphene oxide powder can be greatly improved in functionality, which undoubtedly reduces the application threshold of graphene oxide. In addition, the amount of graphene oxide added at a later stage, the uniformity of dispersion and the degree of compounding with the matrix material are controlled to improve the conductivity of reduced graphene oxide and meet the requirements for conductivity of existing anticorrosive coatings, thereby reducing or replacing the use of metal fillers!
- Thermal conductivity
The high thermal conductivity and large specific surface area undoubtedly lay the foundation for its use as a thermally conductive material. At the same time, the reduction of active sites on graphene oxide improves its usability, and the stable conjugate structure allows it to work at high temperatures.
Although incomplete reduction of graphene oxide has many advantages over graphene in terms of dispersibility and functionalization, it will also introduce some defects and other functional groups at the same time, reducing graphite. The excellent electrical conductivity and corrosion resistance of graphene itself, how to choose a proper function and application, is an important topic that many researchers face. I hope that through continuous research, these problems can be solved!