Spin Selectivity-Based Enantiomeric Discrimination by Chiral Nanostructured Au Films

Photomagnetic-chiral anisotropy (PM-ChAC-E) and surface-enhanced Raman scattering chiral anisotropy (SERS-ChAC-E) are novel enantiomeric discrimination techniques generated by chiroptical response due to the interactions between chiral nanostructured metal films (C) and enantiomers (E). The normal Gauss meter and the Raman scattering spectrometer can be used in these versatile techniques. Here, we report the discrimination mechanism of chiral nanostructured Au films (CNAFs) based on the spin polarization coupling (SPC) between the enantiomers and CNAFs. The CNAFs represent Boerdijk-Coxeter-Bernal helical Au nanofibers with different lengths and widths perpendicularly grown on substrates. The optical activities, magnetic circular dichroism, and magnetic tip conducting atomic force microscopy indicated that the spin selectivity of CNAFs depends on the length of CNAFs. The spin selectivity-dependent selective enhancement of photomagnetic field and Raman scattering suggested that the chirality-induced SPC between the enantiomers and CNAFs gives rise to the phenomena of PM-ChAC-E and consequently SERS-ChAC-E. These findings provide possible mechanism based on spin selectivity in chiral structures and make it a universal theory for enantiomeric discrimination.