AC electric field-induced alignment and long-range assembly of multi-wall carbon nanotubes inside aqueous media.

Journal of nanoscience and nanotechnology · 2007 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 3415

Study snapshot

PublicationJournal of nanoscience and nanotechnology · 2007

Study typeengineering

Reported directionUnclear

Evidence ratingInsufficient

Abstract

The present work examines the behavior of multiwall carbon nanotubes (MWCNT) inside AC electric fields created by three-dimensional electrodes. The response of carbon nanotubes stably suspended in water with the aid of a nonionic surfactant is monitored by combining microscopic observations with on-line measurements of the suspension resistivity. It is found that polarization effects induced by the externally applied AC electric field on MWCNTs can cause their unidirectional orientation and end-to-end contact that result in formations of spatially distributed, long-range, three-dimensional and electrically conducting structures that span the entire gap between the electrodes. The length of the formed structures, which in the present case was approximately 30 times larger than that of an individual carbon nanotube, can be controlled by adjusting the spacing between the electrodes. The influence of main experimental parameters, namely, MWCNT concentration, applied voltage, AC field frequency, and electrode surface topography on the suspension behavior is experimentally examined. Results are demonstrated for applied voltage values, AC field frequencies, and carbon nanotube concentrations in the range 4-40 Vptp, 10 Hz-5 MHz, and 0.001-2.0 wt%, respectively. While higher electric field strengths accelerate the formation of aligned structures, higher frequency values were found to result in suspensions that exhibit smaller electrical resistivity. Carbon nanotube dispersions exposed to an AC electric field exhibit a 100-fold or more decrease in their electrical resistivity, even when carbon nanotube concentrations as low as 0.005 wt% are used.

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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 typeengineering

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Multiwall carbon nanotubes suspended in water aligned unidirectionally and formed long-range, electrically conducting structures spanning the electrode gap when exposed to an externally applied AC electric field. Higher field strengths accelerated formation of aligned structures, and higher AC frequencies were associated with smaller suspension resistivity; exposures produced a 100-fold or greater decrease in electrical resistivity even at low nanotube concentrations (e.g., 0.005 wt%).

Outcomes measured

MWCNT alignment/orientation
End-to-end contact and 3D assembly/structure formation spanning electrode gap
Electrical resistivity of suspension
Effect of voltage, frequency, concentration, electrode surface topography on behavior

Limitations

In vitro/engineering study in aqueous media; no health outcomes assessed
No specific electric field strength (e.g., V/m) reported in abstract (only applied voltage range)
No exposure duration reported
Frequency reported as a range (10 Hz–5 MHz) without specifying values used for each result

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "AC electric field (three-dimensional electrodes)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "MWCNT alignment/orientation",
    "End-to-end contact and 3D assembly/structure formation spanning electrode gap",
    "Electrical resistivity of suspension",
    "Effect of voltage, frequency, concentration, electrode surface topography on behavior"
  ],
  "main_findings": "Multiwall carbon nanotubes suspended in water aligned unidirectionally and formed long-range, electrically conducting structures spanning the electrode gap when exposed to an externally applied AC electric field. Higher field strengths accelerated formation of aligned structures, and higher AC frequencies were associated with smaller suspension resistivity; exposures produced a 100-fold or greater decrease in electrical resistivity even at low nanotube concentrations (e.g., 0.005 wt%).",
  "effect_direction": "unclear",
  "limitations": [
    "In vitro/engineering study in aqueous media; no health outcomes assessed",
    "No specific electric field strength (e.g., V/m) reported in abstract (only applied voltage range)",
    "No exposure duration reported",
    "Frequency reported as a range (10 Hz–5 MHz) without specifying values used for each result"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "AC electric field",
    "multiwall carbon nanotubes",
    "MWCNT",
    "alignment",
    "assembly",
    "aqueous suspension",
    "frequency",
    "voltage",
    "electrical resistivity",
    "electrodes"
  ],
  "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: 10.1166/jnn.2007.871
PubMed: 18283810

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