Enantioselective Asymmetric Generation in Chiral Crystallization from Plasmonic Nanoparticles Optically Trapped by Circularly Polarized Laser

Abstract

We demonstrate that a statistically-significant chiral bias can be observed in NaClO₃ chiral crystallization induced by circularly polarized laser trapping of Ag nano-aggregates at the air/an unsaturated solution. A continuous-wave visible laser (λ = 532 nm) was used as the light source. The "dominant" enantiomorph was switchable by changing the handedness of the circularly polarized laser, indicating that the chiral bias is enantioselective. The resulting crystal enantiomeric excess (CEE) reached approximately 25%. The CEE is much higher than the typical enantiomeric excess (ee) in asymmetric photosynthesis of organic compounds ranging from 0.5 to 2%. The efficient chiral bias may be due to the plasmon-induced circular dichroism by coupling between chiral pre-nucleation crystalline cluster and localized surface plasmon of the Ag nanoparticles. Our results shed a light not only to the mechanism of chiral nucleation but also to evaluation method for ee of chiral compounds synthesized in chiral plasmonic near-field.