A new study led by postdoctoral researchers Stefano Ippolito and Francesca
Urban at Drexel University has uncovered a surprising thermal behavior in a
lesser-studied variant of MXene, a class of two-dimensional materials
discovered at Drexel. Published in Advanced Electronic Materials,
the work reveals that this titanium carbide MXene composition responds to
light in an unexpected way, showing asymmetric and extremely slow thermal
relaxation. This behavior could be harnessed to create innovative optical
memory technologies.
MXenes are ultra-thin nanomaterials (about a hundred thousand times thinner
than a human hair) created by selectively removing atomic layers from
layered ceramics. They are known for their metallic conductivity, high
surface area, and ability to interact with a broad spectrum of
electromagnetic radiation. These properties make them promising candidates
for use in electronics, sensing, communication, and energy systems.
However, most research to date has focused on the first discovered titanium
carbide MXene, while many other compositions remain underexplored due to
difficulties in synthesis and somewhat lower environmental stability.
Ippolito and Urban, working within the A.J. Drexel Nanomaterials Institute,
fabricated thin-film devices from two different titanium-based MXenes and
exposed them to laser irradiation. Although both materials absorbed similar
amounts of light at the selected wavelength, they exhibited strikingly
different photothermal behavior. The best studied material with three
titanium and two carbon atoms in cross-section responded by following a
typical symmetric heating and cooling cycle. The thinner one, with two
titanium and one carbon atom, displayed a highly asymmetric pattern,
heating rapidly but cooling more than a thousand times more slowly.
Environmental conditions, such as temperature and pressure, further
influenced this unusual response, providing additional tools to tune the
device’s performance on demand.
“This is not just a matter of how much light the material absorbs,” said
Ippolito. “It is about how the material stores and releases thermal energy
after light absorption. In this case, one of the materials behaves in a
completely unexpected way.”
The team used this unique behavior to build a proof-of-concept optical
memory device. By varying the length of laser pulses and operating
conditions, they were able to generate and retain distinct current levels
in the devices. These states could be separated with enough precision to
support multi-bit data storage. In one experiment, the MXene device held 18
distinct levels (under ambient conditions), enough to exceed the required
16 levels for 4-bit computing. The states could be reset by increasing the
temperature, enabling a light-write and heat-erase memory system.
Such capabilities could have implications for low-power data storage,
environmental sensing, and neuromorphic computing – systems that mimic the
way the brain processes and stores information.
The study was conducted under the supervision of Yury Gogotsi, PhD,
Distinguished University and Charles T. and Ruth M. Bach Professor, and in
collaboration with Jonathan Spanier, PhD, professor and department head of
Mechanical Engineering and Mechanics. Paolo Samorì, Distinguished Professor
at the Université de Strasbourg, was also a co-author.
The researchers note that the findings point to a broader need for
understanding how different MXene compositions behave, especially as the
field moves faster and toward more targeted, application-driven designs.
“This highlights how much remains to be discovered,” said Urban. “We're
just beginning to understand how composition and structure influence
properties and performance in these complex materials.”