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Author: Mike Williams, Rice University

The blender that mixes the cream into the coffee may not have much effect on the beverage. But in the chemistry laboratory, it turns out that using the wrong stirrer can distort science.

Scientists at Rice University have determined that a stir bar made of PTFE (commonly called Teflon) can introduce errors in standard laboratory reactions used to manipulate the properties of carbon or boron nitride nanotubes.

The stirring rod is a spherical ferromagnetic metal rod covered with polytetrafluoroethylene. It is located at the bottom of the beaker and rotates under the action of a rotating magnetic field. They allow the solution to be mixed in a closed flask without manual stirring.

Angel Martí’s Rice laboratory published a paper in the American Chemical Society journal ACS Omega outlining what happens when a PTFE stir bar is used to reduce functionalized nanotubes through Billups-Birch, a long-term reaction , Part of Billups, which was developed by Rice Professor Emeritus of Chemistry, Emeritus, to release electrons and combine with other atoms.

Reduction is often used to make nanotubes easier to functionalize, that is, the process of adding molecules such as proteins to customize them for use in applications. This can be as simple as dispersing the nanotubes in a chemical bath containing the molecules you want to add. The researchers said that Billups-Birch is one such method, a one-step process for functionalizing nanotubes with various molecules.

When they used it to modify boron nitride nanotubes, the researchers were surprised to find that their tube turned gray, and the PTFE stirring rod turned black. Standard thermogravimetric analysis is usually sufficient to see evidence of functionalization, but no problems are found-but the researchers did.

"Other than that, we can't get consistent results," Martí said. "Sometimes we get very high functionalization-or obvious functionalization-sometimes we don't. It's really weird."

They found that the lithium in the amino solvent used in the Billups-Burch reaction reacted with the white polytetrafluoroethylene in the rods, turning them black.

"Because the carbon nanotubes are black, it is easy to believe that the nanotubes are deposited on the rods throughout the reaction," Marty said. "But this is not the case. We found that under Billups-Birch conditions, PTFE reacts.

"Teflon usually doesn't react with anything," he said. "This is why it is used for stirring rods and cookware. This is why it is easy to overlook what we see in the laboratory."

Martí said that searching the literature did not find that Billups-Burch avoided the use of PTFE.

"It's also very strange," he said. "Maybe everyone else knows-but just in case we decide to explore this question. That's why we decided to write a paper."

Researchers suspect that an accidental reaction with Teflon will produce free radicals, thereby reducing the efficiency of the reaction and possibly attacking boron nitride or carbon nanotubes. At the same time, their quick solution to the problem may be the simplest.

"Now we use glass-coated stirring rods," Martí said. "Glass is completely inert. This provides us with reproducibility and good functionalization." Further explore researchers to enhance boron nitride nanotubes for next-generation composites. More information: Carlos A. de los Reyes, etc. People, the use of Billups–Birch reduction conditions on the adverse effects of carbon and boron nitride nanotubes covalently functionalized PTFE stir bar, ACS Omega (2019). DOI: 10.1021/acsomega.8b03677 Journal information: ACS Omega

Citation provided by Rice University: Strange reaction caused a sensation in the laboratory (2019, March 29) Retrieved on December 6, 2021 from https://phys.org/news/2019-03-odd-reaction- lab.html This document is subject to copyright. Except for any fair transaction for private learning or research purposes, no part may be copied without written permission. The content is for reference only.

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