A device for measuring spin selectivity in electron transfer

Abstract

A new type of device is presented that allows direct measurement of spin selectivity in charge transfer processes occurring in adsorbed molecules. The new device provides direct information about the nature of the charge being transferred (electrons or holes) and on spin selectivity, if it exists. Here the device is applied for establishing the spin-dependent electron transfer through double-stranded DNA and its variation with the length of the oligomer. The DNA is self-assembled on a silver substrate and is measured under ambient conditions. The device is based on monitoring the electric potential between a ferromagnetic Ni layer and a silver layer, on top of which the DNA is self-assembled. When a dye molecule, attached to the DNA, is photoexcited, a charge transfer between the dye and the silver substrate takes place, resulting in a change in the electric potential between the Ni and the silver. If the charge transfer is spin selective, the electric potential measured depends on the direction of magnetization of the Ni.

Spin Selectivity in Electron Transfer in Photosystem I

“…[20,21] The robust PSI, used in these experiments, is isolated from the thylakoid membranes of cyanobacteria and is stable and active when adsorbed in a dry environment. [22] The spin selectivity of the ET process and its temperature dependence were studied by applying a new type of capacitance device [23] (see Figure 1 B-D, and details in SI).…”

“…The values obtained for the polarization, at room temperature, are extremely high and exceed those measured for ET through 78 base long DNA with the same device. [23] The correction procedure, as described in the SI has two parameters, the nonideal spin polarization of the nickel and the silvers Debye temperature. While the error in the first parameter is very small, the actual Debye temperature may vary from sample to sample by about 10 %, as probed in ref.…”

“…While the error in the first parameter is very small, the actual Debye temperature may vary from sample to sample by about 10 %, as probed in ref. 23. This factor introduces large error in the values obtained for the corrected polarization.…”

Spin Selectivity in Electron Transfer in Photosystem I

“…21 The robust PSI, used in these experiments, is isolated from the thylakoid membranes of cyanobacteria and is stable and active when adsorbed in a dry environment 22. The spin selectivity of the ET process and its temperature dependence were studied by applying a new type of capacitance device23 (see Figure 1 B–D, and details in SI).…”

Contact effects in spin transport along double-helical molecules

“…Recent experiments on spin transport along DNA molecules have led to an important breakthrough in molecular spintronics [1][2][3]. Göhler et al reported that the electrons transmitted through self-assembled monolayers of double-stranded DNA (dsDNA) at room temperature were highly polarized and that the spin polarization increased with the DNA length, while spin-dependent effects were not observed in single-stranded DNA (ssDNA) monolayers [1].…”