Scientists have, for the first time, directly measured the intrinsic properties of individual MXene flakes – ultra-thin nanomaterials being explored for applications ranging from flexible electronics to clean energy. The findings, published in ACS Nano, were made possible by a newly developed technique called spectroscopic micro-ellipsometry (SME), which reveals optical, structural, and charge transport properties at the single-flake level.
MXenes, composed of two-dimensional layers of transition metal carbides and nitrides, are just a few atoms thick. While known for high conductivity and energy storage potential, their true behavior had remained obscured due to reliance on bulk analyses of stacked films. That approach, while useful, masked the unique properties of single flakes.
To overcome this limitation, a collaborative team from Helmholtz-Zentrum Berlin and the Hebrew University of Jerusalem designed SME – a method with sub-micron spatial resolution. The system shines polarized light on flakes as small as a single molecular layer, then captures how the reflected signal changes to reconstruct their physical and electronic characteristics.
“Measuring how single MXene flakes depolarize light enabled us to pinpoint structural intra-flake variations in thickness at the nano level,” said Andreas Furchner, who led the project at Helmholtz-Zentrum Berlin, in a press release. “We were excited to see how well the results match destructive techniques like STEM.”
Unlike atomic force or electron microscopy, SME is non-invasive and fast. “In less than one minute, we can directly measure the optical properties, thickness, structural properties, and conductivity of individual MXene flakes,” said Ralfy Kenaz, SME co-developer at Hebrew University. “Normally, these measurements require three different instruments, are time-consuming and destructive, and in the end, not as reliable as spectroscopic micro-ellipsometry.”
The researchers found that thinner MXene flakes have higher electrical resistance – an essential insight for engineering devices with predictable performance. SME also matched high-resolution imaging standards, positioning it as a lab-friendly alternative to synchrotron-based tools.
Beyond MXenes, the technique offers a new way to characterize other two-dimensional materials. “This work provides a roadmap for integrating MXenes into real technologies [...] by offering a direct view of their intrinsic properties,” said Ronen Rapaport of Hebrew University.
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