Rice laboratory experiments refined hexagonal processing of boron nitride.
Just a little soap helps clean the process of preparing the two-dimensional hexagonal boron nitride (hBN).
The University of Rice chemists have found a way to get the maximum 2D hBN nanosheet from its natural mass form by processing it with surfactant (aka soap) and water. Surround surfactants and stabilize microscopic flakes, preserving their properties.
Experiments by Sangu Angel Martí’s chemical laboratory identified the “sweet spot” for spreading hBN stability, which can be processed into a very thin antibacterial film that regulates temperatures up to 900 degrees Celsius (1,652 degrees Fahrenheit).
The work led by Martí, alumni Ashleigh Smith McWilliams and graduate student Cecilia Martínez-Jiménez is complete in the journal American Chemical Society ACS Applied Nano Material.
“Boron nitron materials are attractive, especially because they are very resistant to heat,” said Martí. “It simply came to our notice then graphene and carbon nanotubes, but you can put hBN on fire and nothing happens. “
He said mass hBN is cheap and easy to obtain, but processing into microscopic building blocks has become a challenge. “The first step is to exfoliate and dissolve it, but research on how to do it has spread,” said Martí. “When we decided to set the benchmark, we found a process that was already very useful for graphene and nanotubes did not work well for boron nitride.”
Mass hBN sonication in water successfully removes the material and makes it soluble. “It surprised us, because nanotubes or graphene just float on top,” Martí said. “HBN is spread to all, even though they are unstable.
“It turns out that boron nitride crystal boundaries are made up of amines and nitric oxide and boric groups acid, and all these groups are polar (with a positive or negative charge), “he said.” So when you inflate them, the edges of many of these functional groups are very fond of water. It never happened with graphene. “
Experiments with nine surfactants help them find the right type and amount to keep 2D hBN from clots while not cutting too much of their respective flakes during sonication. Researchers used 1% weight of each surfactant in water, added 20 milligrams of large hBN, then stirred and sonicated the mixture.
Spinning solutions produced at low and high prices indicate the highest yield of surfactant known as PF88 in 100-gravity centrifugation, but high quality nanoseconds came from all ion surfactants under 8,000 g centrifugation, with the greatest stability of common ions surfactants SDS and CTAC.
DTAB – short for dodecyltrimethylammonium bromide – in high centrifugation proved to be the best in balancing yield with 2D hBN quality.
Researchers also produced transparent films from hBN nanosheets that were spread on SDS and water to show how they could be processed into useful products.
“We describe the steps you need to take to produce high quality hBN fragments,” said Martí. “All steps are important, and we are able to understand the consequences of each.”
References: “Understanding the Exfoliation and Dispersion of Hexagonal Boron Nitride Nanosheets by Surfactants: Implications for Antibacterial and Thermally Resistant Coatings” by Ashleigh D. Smith McWilliams, Cecilia Martínez-Jiménez, Asia Matatyaho Ya’akobi, Cedric J. Ginestra, Yeshayahu and Angel A. Martí, January 7, 2021, ACS Applied Nano Material.
DOI: 10.1021 / acsanm.0c02437
The author of the paper is Sed graduate student Cedric Ginestra; Asian graduate students Matatyaho Ya’akobi and Yeshayahu Talmon, professor emeritus of chemical engineering, at the Technion-Israel Institute of Technology; and Matteo Pasquali, professor AJ Hartsook of Chemical and Biomolecular Engineering, chemistry and materials science and nanoengineering at Rice. Martí is a professor of chemistry, biology and materials science and nanoengineering.
The National Science Foundation, the Air Force Office of Scientific Research and the National Council of Science and Technology (CONACyT) of Mexico support the research.