Optical enantioseparation of chiral molecules using asymmetric plasmonic nanoapertures

Using electromagnetic modeling and analytical methods, we study the optimal conditions of an enantioselective optical process (EOP) through the interaction potential between enantiomers and localized chiral near-fields created by asymmetric plasmonic crescent moon (PCM) nanoapertures when it is illuminated with circularly polarized light. We introduce a chiral dissymmetry factor which measures the degree of chiral discrimination of the EOP and we found that it depends mainly on the differential field intensification, near-field optical chirality and the handedness of the enantiomers. Our results prove that a sub-10-nm non-magnetic enantiomer pair of chiral spherical molecules with chirality parameter up to ± 0.005±0.005 can be passively separated under dual-symmetric conditions. The method and the proposed nanostructure may enable all-optical enantioseparation of single-chiral macromolecules, such as proteins and carbohydrates.