Nearly 15 years after discovering MXenes, a versatile class of two-dimensional conductive nanomaterials, researchers at Drexel University have now developed a way to create a one-dimensional version known as MXene nanoscrolls. These ultra-thin structures, about 100 times thinner than a human hair, are even more conductive than their flat counterparts and could significantly improve technologies such as energy storage devices, biosensors, and wearable electronics.
The research, published in the journal Advanced Materials, introduces a scalable method for producing these nanoscrolls from MXene precursors while precisely controlling their shape and chemical composition.
“Two-dimensional morphology is very important in many applications. However, there are applications where 1D morphology is superior,” said Yury Gogotsi, PhD, Distinguished University and Bach professor in Drexel’s College of Engineering, who was a corresponding author of the paper. “It’s like comparing steel sheets to metal pipes or rebar. One needs sheets to make car bodies, but to pump water or reinforce concrete, long tubes or rods are needed.”
From Flat Sheets to Tubular Nanostructures
The team created the nanoscrolls by rolling flat MXene flakes into tiny tubular structures that are about ten thousand times thinner than a water pipe. These tube-like materials can strengthen polymers and metals or guide the movement of ions in batteries and desalination systems with far less resistance.
“With standard 2D MXenes, the flakes lay flat on top of each other, which creates a confined-space and a difficult path for ions or molecules to navigate and move between the layers,” said Teng Zhang, PhD, a postdoctoral researcher in the College of Engineering and co-author of the study. “By converting 2D nanosheets into 1D scrolls, we prevent this nano-confinement effect. The open, tubular geometry effectively creates ‘highways’ for rapid transport, allowing ions to move freely.”
While similar structures made from graphene, such as carbon nanotubes, are already well known, producing consistent, high-quality MXene nanoscrolls has been difficult. MXenes offer advantages over graphene, including richer chemistry, easier processing, and higher conductivity, but earlier attempts to form scrolls often led to uneven results.
Scalable Method for Producing MXene Nanoscrolls
To make the nanoscrolls, researchers start with multilayer MXene flakes. By carefully adjusting the chemical environment, they use water to change the surface chemistry of the material. This triggers a structural imbalance called a Janus reaction, which creates internal strain within the layers. As this strain is released, the layers peel apart and curl into tight scrolls.
The team successfully applied this method to six types of MXenes, including two forms of titanium carbide, as well as niobium carbide, vanadium carbide, tantalum carbide, and titanium carbonitride. They were able to consistently produce 10 grams of nanoscrolls with controlled chemical and physical properties.
Improved Conductivity and Sensing Capabilities
The scroll-like structure not only improves electrical conductivity and mechanical strength, but also changes how the material interacts with molecules. This makes it especially promising for sensing applications and advanced composite materials.
“In a standard stacked 2D structure, the active sites for molecular adsorption are often hidden between layers, making it difficult for molecules, especially large biomolecules to reach them,” Gogotsi said. “The open, hollow structure of the scroll solves this by allowing the analytes easy access to the MXene surface. Combining with the material’s high conductivity and mechanical stiffness, this ensures we get a strong, stable signal. Thus, we envision the use of scrolls in biosensing. The same accessible surface of conductive scrolls may be useful for gas sensors, electrochemical capacitors and other devices that require access of ions and molecules to the surfaces.”
Applications in Wearable Electronics and Smart Textiles
The researchers also see strong potential for MXene nanoscrolls in wearable electronics, also known as ionotronic devices. In these systems, the scrolls could both reinforce materials and improve conductivity. Their rigid structure allows them to anchor within soft polymers, adding strength while maintaining a reliable conductive network.
This combination could lead to stretchable materials that continue to function even under repeated bending and movement.
The team also discovered that the orientation of nanoscrolls in solution can be controlled using an electric field. This means they can be aligned with fibers in textiles, creating more durable and conductive coatings for smart fabrics.
“Imagine manipulating millions of tubules 100 times thinner than a human hair to make them build a wire or stand up vertically to make a brush,” Zhang said. “This is real nanotechnology, as we can manipulate matter at the nanoscale. It is also a critical development for functional textiles, as the scrolls could be incorporated as reinforcement materials in synthetic fibers.”
Superconductivity and Future Quantum Applications
Looking ahead, the researchers plan to further investigate how these nanoscrolls behave at the quantum level, particularly their potential for superconductivity.
“Until now, superconductivity in this class of MXenes was limited to pressed pellets of particles and powders, having never been realized in solution-processed films with mechanical flexibility,” Gogotsi said. “By using niobium carbide scrolls, we observed the change of the material enough to enable superconductivity in free-standing, macroscopic films for the first time. The scrolling process introduces specific lattice strain and curvature that are absent in flat sheets. While the exact physical mechanism is still being explored, we hypothesize that this strain, combined with the continuous 1D structure, stabilizes the superconducting state.”
As interest in quantum materials grows, nanomaterials like MXenes are gaining attention for their ability to improve computing power and data storage. This work marks an important step forward by turning MXene superconductivity into a more practical and usable property.
“Using the methods described in this paper, we can now process superconducting MXenes into flexible films, coatings or wires at room temperature for potential superconducting interconnectors or quantum sensors,” Zhang said. “We expect many other interesting phenomena caused by scrolling and are going to study them.”