Self-assembled monolayers of chiral molecules on metal and semiconducting surfaces have recently demonstrated the capability to filter transmitted electrons depending on spin orientation and the handedness of the molecules. This phenomenon, termed the chiral-induced spin selectivity effect, has renewed interest in probing spin-dependent phenomena in adsorbed chiral molecules, including self-assembled monolayers of double-stranded DNA. While the factors that affect DNA-mediated charge transfer have been extensively studied, the influence of DNA base sequence, GC content, or helical geometry on the spin selectivity in transmitted electrons has not been systematically investigated. We probed the dependence of spin polarization in DNA-mediated charge transfer on nitrogenous base sequence as a means to study spin selectivity in both coherent tunneling and incoherent hopping of charge carriers through helical molecules. Self-assembled monolayers of DNA with varying sequences were formed on multilayer substrates that possess perpendicular magnetic anisotropy, enabling the injection of spin-polarized electrons into the monolayers. The spin-filtering phenomenon was monitored using fluorescence microscopy and photoelectrochemistry by taking advantage of the optical properties of water-soluble perylenediimide derivatives that noncovalently and precisely assemble within double-stranded DNA. Competing charge-transfer pathways that lead to fluorescence or photocurrent generation following photoexcitation of the dye molecules are dependent upon the efficiency of DNA-mediated charge transfer to metal surfaces. This efficiency can be modulated with an external magnetic field used to polarize the spins within the multilayer substrates. Controlling spin transport with light in this manner opens up new opportunities to design device architectures that utilize chiral organic species to generate and to manipulate spin-polarized currents.

Spin selectivity in DNA-mediated charge transport: Base sequence and structure relationships

253rd National Meeting (2017)

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