Experimental evidence of a UV light-induced long-range electric field in nanostructured TiO2 thin films in contact with aqueous electrolytes.

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

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UnclearInsufficient evidencePaper 3568

Study snapshot

PublicationThe journal of physical chemistry. B · 2005

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

Nanostructured TiO(2) thin-film electrodes of controlled thickness were obtained by immobilization of TiO(2) powder (Degussa P25) on SnO(2):F (FTO)-coated glasses by electrophoresis. The photocurrent-potential characteristics of the electrodes in contact with an indifferent aqueous electrolyte, for both front--and backside UV illumination, show the existence of a macroscopic electric field in the electrode region near the FTO substrate. This electric field, which is only photoinduced in the presence of water (it does not appear in TiO(2) dye-sensitized solar cells under visible illumination), apparently disappears when an efficient hole scavenger, like methanol, is added to the aqueous electrolyte. It is attributed to a nonhomogeneous spatial accumulation of photogenerated holes at surface-bound OH radicals resulting from the photooxidation of chemisorbed water molecules. The influence of film thickness and UV illumination mode (front- and backside) on the photoinduced electric field is analyzed by solving the transport equations for diffusion and drift of electrons.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeother

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Photocurrent-potential measurements under UV illumination (front and backside) indicate a macroscopic electric field near the FTO substrate in nanostructured TiO2 thin-film electrodes in contact with an aqueous electrolyte. The field is reported to be photoinduced only in the presence of water and to disappear when methanol is added; it is attributed to nonhomogeneous accumulation of photogenerated holes at surface-bound OH radicals from photooxidation of chemisorbed water.

Outcomes measured

Photoinduced macroscopic electric field in TiO2 thin-film electrodes in aqueous electrolyte
Photocurrent-potential characteristics under front- and backside UV illumination
Effect of methanol (hole scavenger) on photoinduced electric field
Influence of film thickness and illumination mode on photoinduced electric field (modeled via electron diffusion/drift transport equations)

View raw extracted JSON

{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": "UV illumination",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Photoinduced macroscopic electric field in TiO2 thin-film electrodes in aqueous electrolyte",
    "Photocurrent-potential characteristics under front- and backside UV illumination",
    "Effect of methanol (hole scavenger) on photoinduced electric field",
    "Influence of film thickness and illumination mode on photoinduced electric field (modeled via electron diffusion/drift transport equations)"
  ],
  "main_findings": "Photocurrent-potential measurements under UV illumination (front and backside) indicate a macroscopic electric field near the FTO substrate in nanostructured TiO2 thin-film electrodes in contact with an aqueous electrolyte. The field is reported to be photoinduced only in the presence of water and to disappear when methanol is added; it is attributed to nonhomogeneous accumulation of photogenerated holes at surface-bound OH radicals from photooxidation of chemisorbed water.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "TiO2 thin films",
    "nanostructured electrodes",
    "UV illumination",
    "photoinduced electric field",
    "aqueous electrolyte",
    "FTO substrate",
    "photocurrent-potential",
    "hole scavenger",
    "methanol",
    "OH radicals",
    "photooxidation",
    "electron diffusion",
    "electron drift",
    "transport equations"
  ],
  "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/jp050182p
PubMed: 16852255

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