Tunable Chiral Plasmonic Activities Enabled via Stimuli Responsive Micro-Origami

Chiral plasmonic nanomaterials with distinctive circularly polarized light-dependent optical responses over a broad range of frequency have great potential for photonic and biomedical applications. However, it still remains challenging to fabricate 3D plasmonic chiral micro-constructs with readily modulated chiroptical properties over the magnitude of ellipticity, mode frequency, and switchable handedness, especially in the vis-NIR range. In this study, polymeric micro-origami-based 3D plasmonic chiral structures are constructed through self-rolling of gold nanospheres (AuNSs)-decorated polymeric micro-sheets. Spherical AuNSs are assembled as highly ordered linear chains on 2D rectangular micro-sheets by polydimethylsiloxane-wrinkle assisted assembly. Upon rolling the micro-sheets to micro-tubules, the AuNS chains transform into 3D helices. The AuNS-assembled helices induce collective plasmonic modes propagating in a helical manner, leading to a strong chiral response over the vis-NIR range. The circular dichroism (CD) is measured to be as high as hundreds of millidegree, and the position and sign of CD peaks are actively modulated by controlling the orientated angle of AuNS chains, enabled by tuning the collective plasmonic modes. This micro-origami-based strategy incorporates the incompatible 2D assembly technique with 3D chiral structures, opening up an intriguing way toward constructing chiral plasmonic structures and modulating chiroptical effects based on responsive polymeric materials. 3D chiral plasmonic structures are realized through shape-morphing of responsive polymer-based origami. Gold nanospheres (AuNSs) are assembled as large-scale, highly ordered linear chains on 2D rectangular polymer micro-sheets. Upon self-rolling of the sheets into micro-tubules, the AuNSs can be arranged in a 3D helical morphology. Tunable circular dichroism signals over mode frequency, magnitude, and switchable handedness are achieved.image

Automated summary

This study presents a synthetic approach to fabricate 3D plasmonic chiral structures by rolling gold nanospheres-decorated polymer micro-sheets into micro-tubules. The resulting structures exhibit distinctive circularly polarized light-dependent optical responses over a broad range of frequencies, offering great potential for photonic and biomedical applications.