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Growth mechanisms in nanocrystalline lead sulfide by stopped-flow kinetic analysis

Journal of Physical Chemistry C, ISSN: 1932-7447, Vol: 113, Issue: 47, Page: 20246-20251
2009
  • 18
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  • 36
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Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    18
    • Citation Indexes
      18
  • Captures
    36

Article Description

The growth mechanisms of thiolate-capped lead sulfide nanocrystals have been elucidated using stoppedflow UV-visible absorption spectroscopy. Spectra were recorded over the range of 0-45 °C at 48 ms intervals during the first 144 s of reaction between Pb(NO) and NaS in an aqueous solution containing thioglycerol and dithioglycerol capping ligands at pH 11. The spectra were deconvoluted by fitting to three Gaussian curves; the lowest-energy of these corresponded to the first excitonic transition and was used to approximate the average particle radius using a linear relationship between the band gap and the particle diameter for spherical PbS clusters. Kinetic models for oriented attachment (OA) and Ostwald ripening (OR) growth mechanisms were used to interpret the evolution of particle radius with time. Least-squares fitting analysis Revealed that OR was the single dominant mechanism of growth in the low temperature range (0-25 °C), while at higher temperatures (30-45 °C) the mechanism was time dependent: within the first 20 s, growth was predominantly by OR; OA was favored thereafter. Parametric optimization showed that OR was controlled by the dissolution kinetics at the particle-matrix interface. The enthalpy (ΔH) and entropy (ΔS) of activation for the OA process were determined by Eyring treatment to be 12 ± 3 and -160 ± 10 J K-1 mol-1, respectively; the resulting Gibbs free energy of activation (ΔG‡) was 62 ± 6 kJ mol-. The very early stages of nanocrystal growth (<0.5 s) were dominated by nucleation processes, and the kinetic data could be fit to neither OR nor OA models. © 2009 American Chemical Society.

Bibliographic Details

Allison L. Brazeau; Nathan D. Jones

American Chemical Society (ACS)

Materials Science; Energy; Chemistry

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