Time- and polarization-resolved optical spectroscopy of colloidal CdSe nanocrystal quantum dots in high magnetic fields.

The journal of physical chemistry. B · 2005 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 3562

Study snapshot

PublicationThe journal of physical chemistry. B · 2005

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

In an effort to elucidate the spin (rather than charge) degrees of freedom in colloidal semiconductor nanocrystal quantum dots, we report on a series of static and time-resolved photoluminescence measurements of colloidal CdSe quantum dots in ultrahigh magnetic fields up to 45 T. At low temperatures (1.5-40 K), the steady-state photoluminescence (PL) develops a high degree of circular polarization with applied magnetic field, indicating the presence of spin-polarized excitons. Time-resolved PL studies reveal a marked decrease in radiative exciton lifetime with increasing magnetic field and temperature. Except for an initial burst of unpolarized PL immediately following photoexcitation, high-field time-resolved PL measurements reveal a constant degree of circular polarization throughout the entire exciton lifetime, even in the presence of pronounced exciton transfer via Förster energy transfer processes.

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Study typeother

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Static and time-resolved photoluminescence measurements of colloidal CdSe quantum dots in magnetic fields up to 45 T showed that steady-state PL developed a high degree of circular polarization with applied field at 1.5–40 K, consistent with spin-polarized excitons. Time-resolved PL indicated a decrease in radiative exciton lifetime with increasing magnetic field and temperature, and the degree of circular polarization remained constant throughout the exciton lifetime after an initial unpolarized burst following photoexcitation.

Outcomes measured

photoluminescence circular polarization
radiative exciton lifetime
spin-polarized excitons
Förster energy transfer (exciton transfer)

View raw extracted JSON

{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": "static magnetic field (ultrahigh magnetic fields)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "photoluminescence circular polarization",
    "radiative exciton lifetime",
    "spin-polarized excitons",
    "Förster energy transfer (exciton transfer)"
  ],
  "main_findings": "Static and time-resolved photoluminescence measurements of colloidal CdSe quantum dots in magnetic fields up to 45 T showed that steady-state PL developed a high degree of circular polarization with applied field at 1.5–40 K, consistent with spin-polarized excitons. Time-resolved PL indicated a decrease in radiative exciton lifetime with increasing magnetic field and temperature, and the degree of circular polarization remained constant throughout the exciton lifetime after an initial unpolarized burst following photoexcitation.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "CdSe",
    "quantum dots",
    "photoluminescence",
    "circular polarization",
    "spin-polarized excitons",
    "ultrahigh magnetic field",
    "time-resolved spectroscopy",
    "Förster energy transfer",
    "low temperature"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1021/jp051738b
PubMed: 16852944

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