Chiral nanohelmet array films with Three-Dimensional (3D) resonance cavities

Chiral nanohelmet array (NHA) films are prepared via an efficient and low-cost colloidal lithography and exhibit strong chiroptical properties. The chirality can be tailored by the opening-angle of the nanounits in the ultraviolet–visible light range, and optical g-factor reaches about 0.26. Such properties can be attributed to the dissymmetric charge oscillations and electric field distributions. Continuous chiral films can be facilely transferred onto other functional substrates and even, inverted in the transferring process, indicating more flexible application scenarios. Especially, benefiting from the three-dimensional (3D) resonance cavities, change of surrounding environment could further result in distinct surface plasmon (SP) modes, thus diverse chiroptical activities. Label-free enantiodiscrimination of biomolecules was demonstrated based on the chiral resonator with pronounced local superchiral fields. Overall, with strong chirality, excellent tunability, transferability and scalable fabrication, the chiral plasmonic NHA will benefit the study of chiral metamaterials and provide a reliable platform for various photonic applications and label-free chiral sensors.