Dynamically Tunable Chiroptical Activities of Flexible Chiral Plasmonic Film via Surface Buckling

Plasmonic nanoparticle-based chiral materials have attracted great interest due to their strong light-matter interaction and tunable resonance frequency. However, challenges remain in dynamically modulating the chiroptical activities while maintain strong signals. Here, chiral assemblies of gold nanospheres(AuNSs) are achieved via mechanical-induced surface buckling of elastic materials, in which linear chain assemblies of AuNSs transform into to 3D "S-liked" morphology along with the formation of unidirectional wrinkles during buckling. This asymmetrical structure leads to strong chiroptical responses, exhibiting circular dichroism (CD) response over vis-NIR range with signal as high as 2.6 degrees and a g-factor up to 0.11. Furthermore, the configuration of "S-liked" assembly is closely associated with the wrinkle shape, which can be tuned through post-stretching. This method facilitates mechanically induced dynamic and reversible modulation of CD magnitude, as well as switching of signal handedness. Taking advantages of the strong and alterable CD signal, the plasmonic chiral structures demonstrate great potential for multi-channel and dynamically switchable information encryption as a prototype. The strategy, based on manipulating the surface patterns of soft materials, opens up a new design principle for constructing chiral structure and modulating chiroptical activities in a continuously adjustable manner, advancing the development of chiral optical materials.