Spin Selectivity-Based Enantiomeric Discrimination by Chiral Nanostructured Au Films

Abstract

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.

Spin Chiral Anisotropy of Chiral Mesostructured Inorganic Materials with Different Intrinsic Magnetisms

“…Considering the existence of SChA in both CNAFs and chiral molecules under laser irradiation, asymmetric spin polarization coupling (SPC) will be generated when CNAFs are loaded with enantiomeric molecules. , As a result, the PMF of CNAFs will be differently affected by enantiomers, which are denoted as PM-ChA C‑E , illustrating the PM-ChA of CNAFs (C) to enantiomers (E). Meanwhile, the surface-enhanced Raman scattering (SERS) of enantiomers will be differently enhanced by CNAFs with left-handed and right-handed structures, and this phenomenon is defined as SERS chiral anisotropy of enantiomers induced by CNAFs (SERS-ChA C‑E ) . The PM-ChA C‑E effect and SERS-ChA C‑E effect have been applied for enantiomeric discrimination regardless of the size, polarity, or chromophore of enantiomers. , …”

Chiral mesostructured NiFe2O4 films with chirality induced spin selectivity

“…1,2 It has been found that inorganic materials endowed with chirality generate optical, electrical, magnetic, and other special properties, which can have wide applications in chiral sensing, catalysis, and devices. 3–9 Currently, numerous chiral inorganic crystals, including metals, semiconductors, ceramics, and inorganic salts, with different chiral structures, sizes and surface properties, have been synthesized for their interesting chiral response. 10–15…”