Simple, slender aromatic hydrocarbon achieves record pressure sensitivity among molecular materials

Osaka, Japan - Applying pressure to luminescent organic crystals usually brings molecules closer together and weakens their fluorescence. Materials that instead brighten and undergo a large color change are rare, and clear design principles for achieving both responses in simple, rigid aromatic hydrocarbons have been lacking.

Researchers at the University of Osaka and collaborators have now found that crystals of a uniformly slender aromatic hydrocarbon become brighter under pressure while changing their fluorescence from light blue to yellow. Its emission-wavelength sensitivity was the highest reported for a molecular material to date.

The team synthesized two anthracene-substituted phenacene derivatives, a broad chrysene-based molecule and a slender phenanthrene-based molecule. Their crystals were compressed in a diamond anvil cell and examined using fluorescence spectroscopy, Raman spectroscopy, and synchrotron X-ray diffraction at SPring-8, a large-scale synchrotron radiation facility.

Between 0.4 and 1.4 GPa, the slender crystal became 1.7 times brighter. By 3.5 GPa, its emission peak had shifted by 131 nm, from 458 to 589 nm, giving a sensitivity of 37.4 nm/GPa. The spectrum recovered after pressure was released, and the response was reproduced over three compression-decompression cycles.

Synchrotron measurements showed that the crystal contracted by only about 3% along the molecule’s long axis but by more than 10% between molecular layers. The researchers attribute the color shift to pressure-assisted excimer-like emission between neighboring molecules. Increased packing rigidity may also suppress the nonradiative processes that normally weaken fluorescence.

In contrast, the broader chrysene-based crystal simply dimmed under the same pressure range, with only a modest color shift — confirming that the molecule's slenderness, not its size, drives the enhanced and highly sensitive response.

“By choosing a slender molecule, we obtained a crystal whose brightness and color respond strongly to pressure,” says corresponding author Ryusei Oketani of the University of Osaka. “We hope this work will lead to materials that make invisible forces visible through color.”

The findings suggest that a long, uniformly narrow molecular shape could provide a design principle for pressure-responsive light-emitting materials. With further development, such reversible color changes could help visualize forces in mechanical components and structural materials and support high-pressure gauges and anti-counterfeiting technologies.
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The article, “Pressure-induced Fluorescence Enhancement and Highly Sensitive Colour Change of Anthracene-introduced Phenacene Derivatives in Solid State,” was published in Journal of Materials Chemistry C on August 7, 2026 at DOI: https://doi.org/10.1039/d6tc01401a

About The University of Osaka
The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, The University of Osaka is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Website: https://resou.osaka-u.ac.jp/en