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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.


Related in: MedlinePlus

(A) Photoluminescencespectra of CdSe NPs attached to an oligopeptide monolayer (Ala-8)adsorbed onto magnetic substrates, as measured in the presence ofan external magnetic field of 0.35 T pointing either UP (blue curve)or DOWN (red curve). (B) Photoluminescence spectra of CdSe NPs attachedto an achiral 1,16-hexadecane dithiol monolayer adsorbed onto themagnetic substrate measured under identical conditions. The nanoparticleswere excited with a green laser at 514 nm.
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fig2: (A) Photoluminescencespectra of CdSe NPs attached to an oligopeptide monolayer (Ala-8)adsorbed onto magnetic substrates, as measured in the presence ofan external magnetic field of 0.35 T pointing either UP (blue curve)or DOWN (red curve). (B) Photoluminescence spectra of CdSe NPs attachedto an achiral 1,16-hexadecane dithiol monolayer adsorbed onto themagnetic substrate measured under identical conditions. The nanoparticleswere excited with a green laser at 514 nm.

Mentions: In the fluorescence setup, upon photoexcitation of the NPs eitherelectron or hole transfer to the substrate may occur and their ratesdetermine the intensity of the fluorescence. As it was established,whereas the lifetime of the isolated CdSe NPs is of the order of 20to 30 ns, when the NPs are able to transfer electrons from the oligopeptideto a metal substrate, the lifetime is shortened to below 1 ns.20 Hence, the fast charge transfer results in loweringthe fluorescence intensity because it hampers the radiative electron–holerecombination process. As was determined by surface photovoltage (SPV)measurements, in the current Ala8–CdSe hybrid system, holetransfer from the excited NPs to the substrate across the hybrid structuresis more efficient than by electron transfer. Figure 2A shows that photoluminescence intensityis affected by the direction of the magnetization of the substrate.Because the quenching of the fluorescence is due to the transfer ofelectrons from the substrate to the NPs (hole transfer from NPs tosubstrate), when the electron’s spin is parallel to the adsorbedmolecule axis (when the magnet was pointing “UP”), itstransfer is more efficient and as a result photoluminescence intensityget quenched. This observation is consistent with former data showingthe same spin preference also in spin-dependent photoelectron transmissionthrough oligopeptides.21 The average ratioof the PL intensity, as estimated by the area under the curve measuredfor two different directions (the magnet pointing “DOWN”vs “UP”), was found to be 1.4 ± 0.2. These resultsare highly reproducible among five different samples prepared underidentical conditions. Several control experiments were performed whereAla-8 was replaced by achiral 1,16-hexadecane dithiol (DT), biphenyl-4,4′-dithiol(BD), and 4-aminothiophenol; an external magnetic field was applied,keeping the experimental setup identical. The achiral SAM–CdSeNP assembles did not exhibit any effect of the external magnetic fieldon the PL intensity, as shown in Figure 2B and Figure S7, corroborating that the CISS effect arises exclusively from chiralstructures.4


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) Photoluminescencespectra of CdSe NPs attached to an oligopeptide monolayer (Ala-8)adsorbed onto magnetic substrates, as measured in the presence ofan external magnetic field of 0.35 T pointing either UP (blue curve)or DOWN (red curve). (B) Photoluminescence spectra of CdSe NPs attachedto an achiral 1,16-hexadecane dithiol monolayer adsorbed onto themagnetic substrate measured under identical conditions. The nanoparticleswere excited with a green laser at 514 nm.
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Related In: Results  -  Collection

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fig2: (A) Photoluminescencespectra of CdSe NPs attached to an oligopeptide monolayer (Ala-8)adsorbed onto magnetic substrates, as measured in the presence ofan external magnetic field of 0.35 T pointing either UP (blue curve)or DOWN (red curve). (B) Photoluminescence spectra of CdSe NPs attachedto an achiral 1,16-hexadecane dithiol monolayer adsorbed onto themagnetic substrate measured under identical conditions. The nanoparticleswere excited with a green laser at 514 nm.
Mentions: In the fluorescence setup, upon photoexcitation of the NPs eitherelectron or hole transfer to the substrate may occur and their ratesdetermine the intensity of the fluorescence. As it was established,whereas the lifetime of the isolated CdSe NPs is of the order of 20to 30 ns, when the NPs are able to transfer electrons from the oligopeptideto a metal substrate, the lifetime is shortened to below 1 ns.20 Hence, the fast charge transfer results in loweringthe fluorescence intensity because it hampers the radiative electron–holerecombination process. As was determined by surface photovoltage (SPV)measurements, in the current Ala8–CdSe hybrid system, holetransfer from the excited NPs to the substrate across the hybrid structuresis more efficient than by electron transfer. Figure 2A shows that photoluminescence intensityis affected by the direction of the magnetization of the substrate.Because the quenching of the fluorescence is due to the transfer ofelectrons from the substrate to the NPs (hole transfer from NPs tosubstrate), when the electron’s spin is parallel to the adsorbedmolecule axis (when the magnet was pointing “UP”), itstransfer is more efficient and as a result photoluminescence intensityget quenched. This observation is consistent with former data showingthe same spin preference also in spin-dependent photoelectron transmissionthrough oligopeptides.21 The average ratioof the PL intensity, as estimated by the area under the curve measuredfor two different directions (the magnet pointing “DOWN”vs “UP”), was found to be 1.4 ± 0.2. These resultsare highly reproducible among five different samples prepared underidentical conditions. Several control experiments were performed whereAla-8 was replaced by achiral 1,16-hexadecane dithiol (DT), biphenyl-4,4′-dithiol(BD), and 4-aminothiophenol; an external magnetic field was applied,keeping the experimental setup identical. The achiral SAM–CdSeNP assembles did not exhibit any effect of the external magnetic fieldon the PL intensity, as shown in Figure 2B and Figure S7, corroborating that the CISS effect arises exclusively from chiralstructures.4

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.


Related in: MedlinePlus