Spin-Selective Charge Transfer-SERS Driven Label-Free Enantioselective Discrimination of Chiral Molecules on Ag Nanoparticle-Decorated Ni Nanorod Arrays

Enantioselective discrimination is critical in several fields, particularly in pharmaceutics and clinical drug research. Chiral molecules possess unique charge transfer properties, showing an enantioselective preference for electron spin orientation when interacting with the magnetic surface. Here, we developed spin-selective charge transfer (SSCT)-based label-free surface-enhanced Raman scattering (SERS) achiral magnetic substrates for the enantioselective discrimination of chiral molecules without creating asymmetric chiral adsorption sites. The e-beam-based glancing angle deposition (GLAD) technique was utilized to construct achiral magnetic surface-enhanced Raman scattering (SERS) substrates by decorating Ag nanoparticles over Ni nanorods. SERS spectroscopy was carried out on significant enantiomers, including cystine, alanine, and DOPA (l-3-(3,4-dihydroxyphenyl) alanine). An external electromagnet was used to manipulate the magnetic substrate's spin polarization by altering the magnetic field's direction. Subsequently, SERS spectra were acquired. Based on the magnetic field's direction, there is a complementary variation in the intensities of SERS spectra of the enantiomers. The SSCT process between molecule-metal complexes synergized with the magnetic field direction to control the electron spin, leading to SERS-based enantioselective discrimination. This label-free, easy, yet practical approach offers a characteristic paradigm shift from the recent complex approaches for chiral detection and separation.