How much do you know about graphene oxide?

Everyone must have known about graphene for a long time, the Honeycomb structure, excellent mechanical properties, electrical properties, optical properties, etc.and don't talk too much introductions here. What is often discussed with graphene is graphene oxide.So why is graphene oxide present? The author believes that the biggest reason is the dispersion.

Graphene oxide, as its name suggests, is an oxide of graphene, which introduces an active oxygen-containing group onto graphene and is treated to obtain a modified graphene sheet, which increases the active reaction sites and makes graphene oxide more It is easy to carry out surface modification and enriches the means of functionalization, which can effectively improve the compatibility of modified graphene oxide with solvents and polymers, and has a wider application in the field of organic and inorganic composite materials.

For the application of powder materials, the premise is that it can be well dispersed in the system used, and it is best to achieve monodispersion, so that the special properties of the powder material can be truly exerted. However, the graphene material is required to be in the water. It is very difficult to completely disperse, because the graphene material has almost no hydrophilic groups on the surface, but the hydrophilic groups such as hydroxyl groups and carboxyl groups attached to the defects of graphene oxide can make its dispersibility in water better than graphene.

Introduction to preparation methods

At present, the mainstream method for preparing graphene oxide at home and abroad is the Hummers method, and the preparation process can be simply summarized as follows:

1. Adding graphite to a strong acid (concentrated sulfuric acid) and a strong oxidizing agent (potassium permanganate) to obtain graphene oxide;

2. The obtained graphene oxide is removed by magnetic stirring or ultrasonic vibration;

3. Reduction of graphene oxide by chemical reduction/thermal reduction or the like to obtain reduced graphene oxide.

Modification method

1. Functional modification of ATRP (Atom Transfer Radical Polymerization) using an oxygen-containing functional group immobilization initiator on the surface of graphene oxide.

2. Fix the initiator on the graphene oxide carbon skeleton for ATRP functional modification.

3. Functional modification by non-covalent bonding of ATRP polymer with graphene oxide.

Function introduction

Preparation of polymer composites

Graphene oxide can be processed in solution after being functionalized, which is very suitable for the preparation of high performance polymer conforming materials.

Of course, in addition to the preparation of organic composite materials, it is also possible to prepare inorganic graphene oxide composite materials, such as metals, metal oxides, ceramics and the like, which are loaded onto the graphene oxide to make a multifunctional material.

For example, the effect of copper/graphene oxide on the catalytic oxidation of MB, it can be seen from the figure that the composite material has an improved oxidation performance for copper.

Preparation of biomedicine

The larger surface area can be used as a drug carrier, and the drug molecules can be grafted onto the active groups of graphene oxide, and functionalized graphene with good water solubility and biocompatibility can be obtained, and molecules with other functions can also be obtained. Grafting onto graphene oxide to produce graphene with various functions, such as purifying the environment and adsorbing toxic and harmful substances in water, greatly enriching the application of graphene oxide.

Antiseptic

Graphene oxide, like graphene, also has good corrosion resistance. In contrast, graphene oxide has an active site and therefore becomes easier to modify, and can be well dispersed in coatings. Its anti-corrosion mechanism is as follows:

1. Layer stacking of sheet oxide through graphene. Although graphene is a two-dimensional sheet structure, after layer stacking and effective uniform dispersion, a three-dimensional three-dimensional structure can be formed on the surface of the product, and projection onto the surface of the product will result in a filling plane to block oxygen in the environment. And the role of water to achieve anti-corrosion purposes.

2. Graphene oxide has good stability. Its chemical properties are stable, and its properties are stable and unaffected under high temperature, corrosion and high oxygen environment. From the preparation method, we can see that its chemical properties are stable enough to resist corrosion in nature.

3. Good electrical conductivity. Reduced graphene oxide has excellent proton/electron conductivity and extremely low conductivity. It improves the cathodic protection path in anti-corrosion coatings, improves the utilization rate of zinc powder, and thus improves anti-corrosion performance.

4. The two-dimensional graphene oxide sheets are uniformly dispersed in the coating, and each sheet has a different orientation, thereby forming a three-dimensional structure, which effectively blocks the corrosion penetration of water molecules and other media.

Conductive

Firstly, the conductivity of graphene itself is very good. The electron migration rate reaches at room temperature, the resistivity is only, the electrons move in a two-dimensional honeycomb structure, and the carriers in graphene follow a special quantum tunnel. The effect is that there is no backscatter when it encounters impurities, so it is also a cause of superconductivity. Although the conjugated network is destroyed after the functionalization (oxidation) of graphene, the graphene oxide has certain insulating properties, but after the reduction treatment, the reduced graphene oxide which is less conductive than the original graphene can be obtained, although Loss of most of the electrical conductivity, but the treated graphene oxide powder can be greatly improved in functionalization, which is undoubtedly lowering the application threshold of graphene oxide, in addition, the amount of addition of graphene oxide can be passed later. The uniformity of dispersion and the degree of recombination with the matrix material are controlled to improve the electrical conductivity of the reduced graphene oxide, satisfy the requirements of the existing anticorrosive coating for conductivity, thereby reducing or replacing the use of the metal filler!

The Institute of Materials Technology and Engineering of the Chinese Academy of Sciences has successfully broken through the technical bottlenecks in the development and application of graphene-modified anti-corrosion coatings. It is at the international advanced level and has been successfully applied in the fields of national power grid, petrochemical, marine engineering and equipment.

Thermal conduction

The higher thermal conductivity and larger specific surface area undoubtedly lay the foundation for its thermal conductive material. At the same time, the active site on the reduced graphene oxide improves its usability and stable conjugate structure, so that it can work at high temperature. It will improve the service life of the product.

To sum up

Although incompletely reduced graphene oxide has many advantages over graphene in dispersibility and functional construction, it also introduces some defects and other functional groups more or less, reducing the excellent conductivity, corrosion resistance and other properties of graphene itself, and how to choose between functions and applications is a topic that many researchers must face. We hope that through the continuous deepening of research, these problems can be solved!

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