In Situ Exploration of Stimulus-Induced Emission Changes in Mechanochromic Dyes

The development of in situ analysis techniques for visualizing and linking macro- and nanoscopic features of external stimulus-responsive materials is crucial for their rational design and applications. Herein, we investigate the mechanical stress-induced emission changes in electron donor-acceptor type organic dye molecules in solid states through in situ single-particle fluorescence spectroscopy combined with macroscopic and nanoscopic stimulation systems. The change in emission color from green to yellow was attributed to repeated rubbing or scratching of the crystal surface, and not to simple cutting. This change was due to partial amorphization, which changed the intra- and intermolecular charge-transfer interactions of stacked molecules near the surface. We believe that this study will facilitate the efficient design of mechano-responsive materials with finely controlled and responsive properties.

Automated summary

The study investigated the mechanism of emission color change in solid-state dye molecules under mechanical stress using in situ single-particle fluorescence spectroscopy, attributing the change to partial amorphization near the crystal surface. The findings suggest that such changes are not solely due to surface abrasion, but rather alterations in charge-transfer interactions within stacked molecules. This research could aid in the efficient design of mechano-responsive materials with controlled and responsive properties.