The European Physical Journal D

, Volume 43, Issue 1–3, pp 91–95

The colours of nanometric gold

Optical response functions of selected gold-cluster thiolates
  • R. B. Wyrwas
  • M. M. Alvarez
  • J. T. Khoury
  • R. C. Price
  • T. G. Schaaff
  • R. L. Whetten
Structure and Thermodynamics of Free Clusters
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Abstract.

A set of broad-range NIR-vis-UV optical absorption spectra, measured for selected gold-cluster thiolate compounds (GCTs, containing ~20 to 300 Au atoms), is consistently displayed and then analyzed within the dielectric-functions approach. The size-evolution toward `bulk' (Au diameter >3-nm) optical response is thereby clearly demonstrated. The emergence of apparent energy gaps, Eon, for onset of optical absorption, as well as other fine-structure, is consistent with that of a well-quantized metallic electronic structure for the compounds' cores: the onset-band's location Eon and intensity are attributed semiclassically to a circulation-frequency resonance of the Fermi-level electrons. With decreasing cluster-size, an increasing fraction of the integrated (sum-rule) intensity is `missing' from the <4 eV region. This might be explained by the outermost layer consisting of Au(I)thiolate complexes.

PACS.

73.22.-f Electronic structure of nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals 73.22.Lp Collective excitations 36.40.Vz Optical properties of clusters 78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity) 

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Copyright information

© EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007

Authors and Affiliations

  • R. B. Wyrwas
    • 1
  • M. M. Alvarez
    • 1
  • J. T. Khoury
    • 1
  • R. C. Price
    • 1
  • T. G. Schaaff
    • 1
  • R. L. Whetten
    • 1
  1. 1.School of Chemistry & Biochemistry, Georgia Institute of TechnologyAtlantaUSA

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