Giant circular dichroism induced by tunable resonance in twisted Z-shaped nanostructure.

Circular dichroism (CD) is useful in molecular chemistry, pharmaceuticals, and bio-sensing. In this paper, twisted Z-shaped nanostructure (TZN) is proposed to achieve giant CD. The TZN is composed of three vertical and twisted nanorods. Given that the resonance of vertical nanorod is only observable for left circularly polarized light excitation but is subdued for right circularly polarized light excitation, which leads to the giant CD effect approaching 88%. The subdued resonance of vertical nanorod can be excited by rotating the bottom nanorod. The CD properties can be tuned by the length of nanorods and the gap between them. These results would guide the design of plasmonic chiral nanostructures for achieving giant CD effect.