Spin-Selective Charge\nTransfer-SERS Driven Label-Free\nEnantioselective Discrimination of Chiral Molecules on Ag Nanoparticle-Decorated\nNi Nanorod Arrays

Enantioselective discrimination is critical in several\nfields,\nparticularly in pharmaceutics and clinical drug research. Chiral molecules\npossess unique charge transfer properties, showing an enantioselective\npreference for electron spin orientation when interacting with the\nmagnetic surface. Here, we developed spin-selective charge transfer\n(SSCT)-based label-free surface-enhanced Raman scattering (SERS) achiral\nmagnetic substrates for the enantioselective discrimination of chiral\nmolecules without creating asymmetric chiral adsorption sites. The\ne-beam-based glancing angle deposition (GLAD) technique was utilized\nto construct achiral magnetic surface-enhanced Raman scattering (SERS)\nsubstrates by decorating Ag nanoparticles over Ni nanorods. SERS spectroscopy\nwas carried out on significant enantiomers, including cystine, alanine,\nand DOPA (l-3-(3,4-dihydroxyphenyl) alanine). An external electromagnet\nwas used to manipulate the magnetic substrate’s spin polarization\nby altering the magnetic field’s direction. Subsequently, SERS\nspectra were acquired. Based on the magnetic field’s direction,\nthere is a complementary variation in the intensities of SERS spectra\nof the enantiomers. The SSCT process between molecule–metal\ncomplexes synergized with the magnetic field direction to control\nthe electron spin, leading to SERS-based enantioselective discrimination.\nThis label-free, easy, yet practical approach offers a characteristic\nparadigm shift from the recent complex approaches for chiral detection\nand separation.