What Makes Graphene Oxide a Key Material in Modern Research? ✨

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Graphene oxide is one of the most exciting material in the field of nanotechnology. It is a derivative of graphene that consists of a single layer of carbon atoms with oxygen-containing functional groups such as hydroxyl, epoxy, and carboxyl groups. These functional groups make GO highly hydrophilic and dispersible in water. Due to its tunable surface properties, it can be applied in various fields, including water purification, energy storage, biomedicine, and flexible electronics. In this article, we’ll explore how graphene oxide is synthesized and its properties.

The structure of GO with functional groups

Figure 01: The structure of GO with functional groups

How Is Graphene Oxide Synthesized?

Graphene oxide is synthesized by oxidizing graphite and then exfoliating it into thin layers. The most widely used method for synthesizing graphene oxide is the Hummers method. This method is suitable for large-scale production because it produces a high yield of graphene oxide. In this method, first graphite powder is mixed with sodium nitrate (NaNO3), and the acid mixture of sulfuric acid (H2SO4) and posporic acid (H3PO4) is added to that. An acid mixture is used as an acidic environment to facilitate the oxidation. Then the mixture is stirred and cooled to prevent overheating. Then the oxidizing agent KMnO4 is slowly added to the mixture while maintaining a low temperature (below 60 °C) to control the exothermic reaction. The mixture is then continuously stirred for around 12 hours to allow the oxidation process. After the oxidation process is done, add H2O2 to the solution to remove residual permanganate (MnO4-) and manganese dioxide (MnO2), resulting in a bright yellow solution. Then the mixture is repeatedly washed with deionized water, ethanol, and hydrochloric acid (HCl) to remove the byproducts. The graphene oxide is then separated by centrifugation. The final result, graphene oxide dispersion, is then freeze-dried.

What Are the Key Properties of Graphene Oxide?

Graphene oxide has several unique properties that make it highly desirable in research and industrial applications. These properties arise due to the presence of oxygen-containing functional groups and the layered structure of graphene oxide. 

Graphene oxide has functional groups such as carboxylic (-COOH), hydroxyl (-OH), and epoxy (-O-). These functional groups are distributed on the surface of the graphene oxide layers, and they are very reactive, so they cause chemical modifications through covalent and non-covalent bonds. This is because the functional groups introduce polar sites on the graphene oxide sheets. Graphene oxide is highly hydrophilic (strong affinity to water) and dispersible in water due to these oxygen-containing functional groups because functional groups and water molecules have strong interactions, mainly hydrogen bonds. And also because of its layered structure, it has a high surface area.

GO also has a mechanical strength similar to graphene, but due to the disruption of its sp²-hybridized carbon network, its mechanical strength is slightly lower than graphene.

Graphene oxide is considered an insulator due to the disruption of sp² hybridization in the graphene oxide layers. However, its conductivity can be increased by removing functional groups from the graphene oxide layers; the result is known as reduced graphene oxide (rGO). Additionally, the disruption of sp² hybridization results in lower thermal conductivity compared to graphene. 

The diverse properties of graphene oxide make it a highly versatile material. Ongoing research continues to explore new ways to enhance its properties and expand its potential uses.

In the next article, we will explore the applications of graphene oxide, discuss their future directions, and highlight the limitations in the field. Thank you for reading. Have a great day! We will see you in the next article.

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