Researchers from the Hebrew University of Jerusalem and the Helmholtz-Zentrum Berlin have for the first time measured the true properties of individual MXene flakes — an exciting new nanomaterial with potential for better batteries, flexible electronics, and clean energy devices.
By using a novel light-based technique called spectroscopic micro-ellipsometry, they discovered how MXenes behave at the single-flake level, revealing changes in conductivity and optical response that were previously hidden when studying only stacked layers. This breakthrough provides the fundamental knowledge and tools needed to design smarter, more efficient technologies powered by MXenes.
MXenes (pronounced max-eens) are ultra-thin materials only a few atoms thick, celebrated for their ability to conduct electricity, store energy, and interact with light. Until now, however, most studies examined MXenes in bulk form — as thin films made up of many overlapping flakes. That approach, while useful, masked the unique properties of single flakes, leaving unanswered questions about their true potential.
The new study was led by Dr. Andreas Furchner from Helmholtz-Zentrum Berlin (HZB), together with Dr. Ralfy Kenaz from the Hebrew University’s (HUJI’s) Institute of Physics — a strong collaboration between the research groups of Dr. Tristan Petit and Prof. Ronen Rapaport, respectively. It reveals, for the first time, how individual MXene flakes behave when isolated and studied at the nanoscale. The findings were recently published in ACS Nano, one of the world’s leading nanoscience and nanotechnology journals.
Ellipsometry is one of the most advanced non-invasive optical techniques for material characterization. However, conventional ellipsometers inherently struggle to measure areas smaller than 50 microns — roughly the width of a human hair — making them unsuitable for analyzing the microscopic structures common in modern technology and research. As a result, ellipsometry measurements on MXenes have been limited to macroscopic thin films made of stacked, overlapping flakes. This limitation has prevented direct measurements of individual MXene flakes, whose lateral dimensions are much smaller, thereby hindering a true understanding of their intrinsic properties.
To crack the problem, the researchers employed an advanced, patented technique they developed and call spectroscopic micro-ellipsometry (SME) — essentially a kind of “optical fingerprinting” — which allowed them to measure the optical, structural, and electronic properties of single MXene flakes with high lateral resolution and without damaging them. In the study, individual MXene flakes of varying thicknesses were synthesized in HZB and sent to HUJI for SME measurements. Complementary nanoscale measurements were performed at HUJI’s Nano Center, and all data analyses were carried out collaboratively by both groups.
By shining light with defined polarization states on microscopic flakes as thin as a single molecular layer and analyzing how that light reflected back, the researchers mapped how the material’s ability to conduct electricity and interact with light changes depending on thickness and structural properties. They discovered that as MXene flakes become thinner, their electrical resistance increases — a critical insight for building reliable, high-performance devices.
The method was so precise that it matched nanoscale imaging tools like atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM), confirming its power as a non-invasive diagnostic tool.