The copper AFM probe can manipulate matter, including organic molecules, at the atomic scale. Image: 2020 Shiotari et al.Nanographene has the potential to radically improve solar cells, fuel cells, LEDs and more, but the synthesis of this 2D material has proved difficult to control. For the first time, researchers have now discovered a simple way to gain precise control over the fabrication of nanographene. In so doing, they have shed light on the previously unclear chemical processes involved in nanographene production. The researchers report their findings in a paper in Nano Letters.
Graphene is the one-atom-thick sheet of carbon molecules forecast to revolutionize many technologies. Units of graphene are known as nanographene; these are tailored to specific functions and, as such, their fabrication process is more complicated than that of generic graphene. Nanographene is made by selectively removing hydrogen atoms from organic molecules of carbon and hydrogen, a process called dehydrogenation.
"Dehydrogenation takes place on a metal surface such as that of silver, gold or copper, which acts as a catalyst, a material that enables or speeds up a reaction," explained Akitoshi Shiotari, an assistant professor in the Department of Advanced Materials Science at the University of Tokyo in Japan. "However, this surface is large relative to the target organic molecules. This contributes to the difficulty in crafting specific nanographene formations. We needed a better understanding of the catalytic process and a more precise way to control it."
Through exploring various ways to perform nanographene synthesis, Shiotari and his team have come up with a method that offers precise control and is also very efficient. The researchers utilized a specialized kind of microscope called an atomic force microscope (AFM), which measures details of molecules with a nanoscopic needle-like probe. This probe can be used not only to detect certain characteristics of individual atoms, but also to manipulate them.
"We discovered that the metal probe of the AFM could break carbon-hydrogen bonds in organic molecules," said Shiotari. "It could do so very precisely given its tip is so minute, and it could break bonds without the need for thermal energy. This means we can now fabricate nanographene components in a more controlled way than ever before."
To verify what they were seeing, the team repeated this process with a variety of organic compounds, including two organic molecules called benzonoids and nonbenzonoids with very different structures. This demonstrates that the AFM probe can pull hydrogen atoms from different kinds of materials. Such a detail is important if this method is to be scaled up into a commercial means of production.
"I envisage this technique could be the ultimate way to create functional nanomolecules from the bottom up," said Shiotari. "We can use an AFM to apply other stimuli to target molecules, such as injecting electrons, electronic fields or repulsive forces. It is thrilling to be able to see, control and manipulate structures on such an incredibly miniscule scale."
This story is adapted from material from the University of Tokyo, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.