Chiral Semiconductor Nanostructures Fabricated by Near-Field Photocatalysis with Circularly Polarized UV Light

Chiral nanostructures are attracting increasing attention, as they can be applied to metamaterials and metasurfaces as well as enantioselective sensors and other optoelectronic devices. Recently, a photonic nanofabrication technique has been developed that enables straightforward fabrication of right- and left-handed chiral plasmonic metal nanostructures depending on the handedness of the circularly polarized light (CPL) used. In the present work, we present a fabrication method for chiral semiconductor nanostructures based on local photocatalytic reactions coupled with Mie-type resonances via optical near fields. Simulations of the optical near fields around polygonal ZnO nanoplates, used as achiral and anisotropic semiconductor precursors, revealed twisted near-field distributions under CPL. Single and stacked hexagonal ZnO nanoplates were experimentally synthesized, and Co₃O₄ was deposited onto them via photocatalysis driven by UV-CPL. The stacked ZnO nanoplates were converted to three-dimensional spiral ZnO-Co₃O₄ nanostructures, which exhibited significant circular dichroism.