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Photospintronics: Magnetic Field-Controlled Photoemission and Light-Controlled Spin Transport in Hybrid Chiral Oligopeptide-Nanoparticle Structures.

Mondal PC, Roy P, Kim D, Fullerton EE, Cohen H, Naaman R - Nano Lett. (2016)

Bottom Line: It is shown here that in systems in which organic molecules and semiconductor nanoparticles are combined, matching these technologies results in interesting new phenomena.We report on light induced and spin-dependent charge transfer process through helical oligopeptide-CdSe nanoparticles' (NPs) architectures deposited on ferromagnetic substrates with small coercive force (∼100-200 Oe).By switching the direction of the magnetic field of the substrate, the PL intensity could be alternated.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel.

ABSTRACT
The combination of photonics and spintronics opens new ways to transfer and process information. It is shown here that in systems in which organic molecules and semiconductor nanoparticles are combined, matching these technologies results in interesting new phenomena. We report on light induced and spin-dependent charge transfer process through helical oligopeptide-CdSe nanoparticles' (NPs) architectures deposited on ferromagnetic substrates with small coercive force (∼100-200 Oe). The spin control is achieved by the application of the chirality-induced spin-dependent electron transfer effect and is probed by two different methods: spin-controlled electrochemichemistry and photoluminescence (PL) at room temperature. The injected spin could be controlled by excitation of the nanoparticles. By switching the direction of the magnetic field of the substrate, the PL intensity could be alternated.

No MeSH data available.


A scheme describing theeffect of the light on the spin selectivity. Before excitation (A),the NPs are positively charged and electrons are transferred withtheir spin aligned parallel to their velocity. In the reduction partof the electrochemical process electrons move from the FM cobalt substrate(Co) through the helical molecule to the NPs and from there to theredox couple present in solution. In the oxidation stage, the electronsare transferred from the redox couple to the NPs and from there tothe Co. When NPs are photoexcited (B), because of the hole being transferredfrom the NPs to the Co the NP is now negatively charged. Hence, theelectric field on the chiral molecule is in the opposite directionand now electrons with spin antiparallel to their velocity are transferredpreferentially. The electrochemical process is similar to the electronstransmitted through the NPs to the redox couple in solution.
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fig5: A scheme describing theeffect of the light on the spin selectivity. Before excitation (A),the NPs are positively charged and electrons are transferred withtheir spin aligned parallel to their velocity. In the reduction partof the electrochemical process electrons move from the FM cobalt substrate(Co) through the helical molecule to the NPs and from there to theredox couple present in solution. In the oxidation stage, the electronsare transferred from the redox couple to the NPs and from there tothe Co. When NPs are photoexcited (B), because of the hole being transferredfrom the NPs to the Co the NP is now negatively charged. Hence, theelectric field on the chiral molecule is in the opposite directionand now electrons with spin antiparallel to their velocity are transferredpreferentially. The electrochemical process is similar to the electronstransmitted through the NPs to the redox couple in solution.

Mentions: Figure 5 presents a scheme that explains the experimentalobservations. Before photoexcitation (Figure 5A), the NPs are positively charged, as observedby the XPS measurements that indicate that the work function of thesurface decreases by 105 meV upon the NPs attachment to the functionalpolypeptide monolayers (see Table S3).The PL studies are consistent with the electrons being transferredwith their spin aligned parallel to their velocity. This observationis consistent with former studies on spin-dependent electron transmissionthrough the same oligopeptides.10 In thereduction process of the electrochemical measurements, electrons movefrom the cobalt substrate (Co) through the helical molecule to theNPs and thereafter to the redox couple in solution. In the oxidationprocess a reverse field is applied and the electrons are transferredin the opposite direction from the redox couple to the NPs and fromthere to Co; as a result, the same spin is preferred for electronstransferred from the NPs to the Co. When the NPs are photoexcited,a hole is transferred from the NPs to the Co substrate and the NPsare now negatively charged (Figure 5B). Chemically resolved electrical measurements (CREM)data show a prominent response of the peptide–CdSe NP structuresto light illumination at 630 nm. A decrease in the binding energiesof the Cd line by 120 meV under light, as compared with the same valuerecorded in the dark, results in a clear manifestation of the excitedstate hole transfer to the substrate and creates a negative chargeover the NPs (Figure S6 and Table S3).Hence, the electric field on the chiral molecule is of the oppositedirection and now electrons with spin antiparallel to their velocityare transferred. The electrochemical process is similar as in thedark with the electrons transmitted between the substrate and theredox couple in solution through the NPs.


Photospintronics: Magnetic Field-Controlled Photoemission and Light-Controlled Spin Transport in Hybrid Chiral Oligopeptide-Nanoparticle Structures.

Mondal PC, Roy P, Kim D, Fullerton EE, Cohen H, Naaman R - Nano Lett. (2016)

A scheme describing theeffect of the light on the spin selectivity. Before excitation (A),the NPs are positively charged and electrons are transferred withtheir spin aligned parallel to their velocity. In the reduction partof the electrochemical process electrons move from the FM cobalt substrate(Co) through the helical molecule to the NPs and from there to theredox couple present in solution. In the oxidation stage, the electronsare transferred from the redox couple to the NPs and from there tothe Co. When NPs are photoexcited (B), because of the hole being transferredfrom the NPs to the Co the NP is now negatively charged. Hence, theelectric field on the chiral molecule is in the opposite directionand now electrons with spin antiparallel to their velocity are transferredpreferentially. The electrochemical process is similar to the electronstransmitted through the NPs to the redox couple in solution.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834632&req=5

fig5: A scheme describing theeffect of the light on the spin selectivity. Before excitation (A),the NPs are positively charged and electrons are transferred withtheir spin aligned parallel to their velocity. In the reduction partof the electrochemical process electrons move from the FM cobalt substrate(Co) through the helical molecule to the NPs and from there to theredox couple present in solution. In the oxidation stage, the electronsare transferred from the redox couple to the NPs and from there tothe Co. When NPs are photoexcited (B), because of the hole being transferredfrom the NPs to the Co the NP is now negatively charged. Hence, theelectric field on the chiral molecule is in the opposite directionand now electrons with spin antiparallel to their velocity are transferredpreferentially. The electrochemical process is similar to the electronstransmitted through the NPs to the redox couple in solution.
Mentions: Figure 5 presents a scheme that explains the experimentalobservations. Before photoexcitation (Figure 5A), the NPs are positively charged, as observedby the XPS measurements that indicate that the work function of thesurface decreases by 105 meV upon the NPs attachment to the functionalpolypeptide monolayers (see Table S3).The PL studies are consistent with the electrons being transferredwith their spin aligned parallel to their velocity. This observationis consistent with former studies on spin-dependent electron transmissionthrough the same oligopeptides.10 In thereduction process of the electrochemical measurements, electrons movefrom the cobalt substrate (Co) through the helical molecule to theNPs and thereafter to the redox couple in solution. In the oxidationprocess a reverse field is applied and the electrons are transferredin the opposite direction from the redox couple to the NPs and fromthere to Co; as a result, the same spin is preferred for electronstransferred from the NPs to the Co. When the NPs are photoexcited,a hole is transferred from the NPs to the Co substrate and the NPsare now negatively charged (Figure 5B). Chemically resolved electrical measurements (CREM)data show a prominent response of the peptide–CdSe NP structuresto light illumination at 630 nm. A decrease in the binding energiesof the Cd line by 120 meV under light, as compared with the same valuerecorded in the dark, results in a clear manifestation of the excitedstate hole transfer to the substrate and creates a negative chargeover the NPs (Figure S6 and Table S3).Hence, the electric field on the chiral molecule is of the oppositedirection and now electrons with spin antiparallel to their velocityare transferred. The electrochemical process is similar as in thedark with the electrons transmitted between the substrate and theredox couple in solution through the NPs.

Bottom Line: It is shown here that in systems in which organic molecules and semiconductor nanoparticles are combined, matching these technologies results in interesting new phenomena.We report on light induced and spin-dependent charge transfer process through helical oligopeptide-CdSe nanoparticles' (NPs) architectures deposited on ferromagnetic substrates with small coercive force (∼100-200 Oe).By switching the direction of the magnetic field of the substrate, the PL intensity could be alternated.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel.

ABSTRACT
The combination of photonics and spintronics opens new ways to transfer and process information. It is shown here that in systems in which organic molecules and semiconductor nanoparticles are combined, matching these technologies results in interesting new phenomena. We report on light induced and spin-dependent charge transfer process through helical oligopeptide-CdSe nanoparticles' (NPs) architectures deposited on ferromagnetic substrates with small coercive force (∼100-200 Oe). The spin control is achieved by the application of the chirality-induced spin-dependent electron transfer effect and is probed by two different methods: spin-controlled electrochemichemistry and photoluminescence (PL) at room temperature. The injected spin could be controlled by excitation of the nanoparticles. By switching the direction of the magnetic field of the substrate, the PL intensity could be alternated.

No MeSH data available.