Expanding The Graphene Toolkit

Scientists have developed a way to make graphene more reactive so that different chemical groups can be attached to fine tune its properties.

AsianScientist (Apr. 17, 2017) – Researchers have develop a method to increase the range of uses for graphene by ‘decorating’ its surface with different functional groups. These findings, published in the Journal of the American Chemical Society, show how both single and bilayer graphene can be used as a platform to produce 2D materials with novel characteristics.

Graphene—a single layer of carbon atoms packed in a honeycomb lattice—is one of the most versatile materials ever made. The properties of graphene can be tuned by adding on different chemical groups in a process known as functionalization. An area of extensive research interest, functionalized graphene could be used in transistors, sensors, supercapacitors, drug delivery, flexible electrodes and polymer nanocomposites.

In previous research, scientists have successfully functionalized single layered graphene supported on silica or silicon. However, functionalizing bilayer graphene has proven to be much more difficult. The two graphene layers adhere to each other through what are known as van der Waals forces, making bilayer graphene more chemically stable and unreactive.

To study how bilayer graphene can be functionalized, researchers at the Center for Multidimensional Carbon Materials, within the Institute for Basic Science (IBS) at Ulsan National Institute of Science and Technology (UNIST) used a mixture of sodium-potassium alloy and a ring-shaped crown ether molecule (15-crown-5) in tetrahydrofuran. This solution forms negatively charged sodium ions that reduce graphene by donating electrons to it, allowing both single and bilayer graphene to react with other molecules more easily.

Using this reaction, the researchers demonstrated that although bilayer graphene is less reactive than single layer graphene, both of them can be functionalized. Moreover, by using bilayer graphene with one layer of normal carbon and another layer of carbon isotope-labeled carbon (13C), the scientists showed that both the upper and lower layers of graphene are decorated.

The team also showed that functionalized graphene can undergo further chemical reactions with other molecules. For example, graphene functionalized with 4-iodopyridine can then further react with benzyl bromide. This is a particularly interesting approach, since graphene decorated with benzyl bromide can be used for sensors and can be decorated with more chemical groups, greatly expanding the ‘toolkit’ of options.

“We envision that this method and platform will contribute to expanding the application range of graphene,” said study corresponding author Rodney S. Ruoff, UNIST Distinguished Professor and Director of the Center for Multidimensional Carbon Materials.

The article can be found at: Biswal et al. (2017) Sodide and Organic Halides Effect Covalent Functionalization of Single-Layer and Bilayer Graphene.


Source: Institute for Basic Science; Photo: Shutterstock.
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