Materials scientists are investigating the unique physical characteristics of MXenes, a rapidly expanding group of two-dimensional substances with numerous potential applications in nanotechnology.
A research team from the University of Nebraska-Lincoln is delving into the physical features of MXenes, which are a quickly emerging category of two-dimensional materials that hold promise for various nanotechnology uses.
This team’s research builds upon nearly twenty years of work regarding graphenes, another class of 2D materials that are valuable across many fields but show some limitations when compared to MXenes (pronounced “maxenes”).
MXenes consist of ultra-thin layers of transition metal carbides, nitrides, or carbonitrides. They are derived from what is known as the MAX phase, characterized by its three main elements: “M,” which stands for a transition metal like titanium or chromium; “A,” representing elements like aluminum; and “X,” denoting carbon or nitrogen. These components create a layered structure. Chemists have utilized acidic solutions to selectively remove the “A” layers to produce MXenes, making this a straightforward and efficient method.
A variety of MXenes featuring different configurations of “M” and “X” elements have been synthesized. The Nebraska team has concentrated on a lesser-known variant containing chromium, titanium, and carbon atoms, according to Alexander Sinitskii, professor of chemistry and the lead researcher.
“This field is expanding rapidly,” Sinitskii noted.
MXenes have demonstrated their utility in various applications including energy storage, water purification, electromagnetic interference shielding, biomedical uses, and beyond.
These materials’ effectiveness is attributed to their chemical and structural diversity, as well as their ability to be scalable and processed, explained Sinitskii, who is also involved with the Nebraska Center for Materials and Nanoscience, a nationally recognized center that leverages research expertise from three out of the four University of Nebraska campuses.
MXenes feature a high surface area and are easily modifiable. They exhibit a strong interaction with light and are hydrophilic (water-attracting) due to the presence of oxygen and hydroxyl groups on their surfaces.
Sinitskii’s research team has found that the MXene made from chromium and titanium possesses “a specific set of properties not observed in other MXenes.” Prior work from the Nebraska team on different MXene materials indicated their n-type (electron-rich) nature and reduced conductivity under light exposure. In contrast, this new variant is the first MXene to show p-type (electron-deficient) behavior alongside an increase in conductivity when illuminated.
“These characteristics are quite rare for MXenes,” Sinitskii stated. “Many electronic applications require both n-type and p-type materials to function together. While earlier studied MXenes were only n-type, we now present the first p-type MXene. This paves the way for intricate configurations where complementary MXenes can work together to create new electronic capabilities.”
The team has also achieved the production of larger and more uniform flakes of the chromium/titanium carbide MXene than available previously, thus facilitating easier research and application.
The findings of this study were published in the October 1 edition of the journal Matter.
Other contributors from Husker include Saman Bagheri, postdoctoral research associate, chemistry; Michael J. Loes, graduate student, chemistry; Haidong Lu, research assistant professor, physics, and astronomy; Rashmeet Khurana, graduate student, chemistry; Md. Ibrahim Kholil, graduate student, chemistry; and Alexei Gruverman, Mach Professor of physics and astronomy. Co-authors from the South Dakota School of Mines and Technology include Alexey Lipatov, Khimananda Acharya, and Tula R. Paudel.
