Reinforced Room-Temperature Spin Filtering in Chiral Paramagnetic Metallopeptides

Abstract

Chirality-induced spin selectivity (CISS), the effect of helical molecules acting as room temperature hard magnets that confer spin polarization to electrical current, is an intriguing effect with potential applications in nanospintronics. In this scenario, molecules that are paramagnetic as well as helical would introduce a new degree of freedom in the same nano-scale device that has not been explored so far. Here, in order to investigate this idea, we propose the preparation of self-assembled monolayers (SAMs) based on a helical lanthanide binding tag peptide (LnLBTC) on a ferromagnetic substrate. We confirmed room temperature spin filtering of LnLBTC SAMs by well-established electrochemical approach and by direct local spin transport measurements in solid state devices. The latter were studied by a common liquid-metal drop electron transport system, easily implemented for spin dependent measurements. Electrochemistry shows an averaged spin polarization (SP) of ~5% in presence of a saturation magnetic field (H = 350 mT) while local measurements performed in solid state showed a SP of ~50 20% thanks to the reduction of the contribution of pure electron transport in non-covered areas. Calculations showed that conduction electrons interact strongly with the coordinated lanthanide ion, meaning a fixed chirality-based spin filtering can coexist with a spin filtering that is dependent on the polarization of the magnetic metal ion. This opens the door to all-organic single-molecule memristive devices.

Towards peptide-based tunable multistate memristive materials

“…48 Following this idea, we recently showcased the combination of these features in the first report of spin filtering in a solid-state device based on a self-assembled monolayer prepared with Tb 3+ coordinated by an LBT peptide. 49 The active role of the paramagnetic ion was unambiguously confirmed by three independent experimental approaches: cyclic voltammetry (see Fig. 3, right), electrochemical impedance spectroscopy and local transport in solid state devices using liquid-metal drop contacts (see Fig.…”

“…However, LBTs are more specific, moreover it is only in LBTs that a spintronic effect has been experimentally demonstrated due to the interaction between the current flowing through the chiral biomolecule and the paramagnetic lanthanide ion. 49 For the ordering of LBTs at least two other approaches are conceivable (for a more detailed discussion, see SI section S4):…”

“…3 Left: Structure of the LBT peptide complexed with Tb 3+ (green sphere). Right: Depiction of one of the the spintronic devices used to detect the interaction between CISS and the paramagnetic Tb 3+ ion (reproduced with permission from 49 ).…”

The Importance of Spin State in Chiral Supramolecular Electronics

“…Their results showed that the quantum yield of photoelectrons depended both on the relative polarization of the light, and the chirality of the molecules. They started the study of the main factors that influence the CISS effect using self-assembled monolayers (SAMs) of double-stranded (ds) DNA and oligopeptides, demonstrating that spin selectivity is correlated to the supramolecular organization of single molecules, and its magnitude increases with the length of the DNA strands or peptide sequence, respectively ( Carmeli et al, 2002 ; Ray et al, 2006 ; Göhler et al, 2011 ; Xie et al, 2011 ; Kettner et al, 2015 ; Aragonès et al, 2017 ; Kiran et al, 2017 ; Tassinari et al, 2018 ; Torres-Cavanillas et al, 2020 ). These studies pointed out the previously ignored role of the spin in electron-biomolecule interactions, as well as the potential of SAMs of chiral molecules that work as spin filters at room temperature ( Michaeli et al, 2016 ; Naaman et al, 2019 ).…”

Electrochemical Potential‐Driven High‐Throughput Molecular Electronic and Spintronic Devices: From Molecules to Applications

“…This phenomenon is popularly known as the chirality-induced spin selectivity (CISS) effect. [137,[163][164][165][166] Mondal et al reported the formation of monolayer-scale chiral conducting polymer films using poly{[methyl N-(tert-butoxycarbonyl)-(S)-3-thienyl-L-cysteinate]-co-thiophene} (PCT-L), via electrochemical grafting on aNielectrode in the applied potential range of À0.1 to À0.8 Vvs. SCE (saturated calomel electrode) at 50 mV s À1 .…”