The colours of nanometric gold
- First Online:
- 419 Downloads
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)
Unable to display preview. Download preview PDF.
- For recent reviews, see: J.C. Love, L.A. Estroff, J.K. Kriebel, R.G. Nuzzo, G.M. Whitesides, Chem. Rev. 105, 1103 (2005); M. Daniel, D. Astruc, Chem. Rev. 104, 293 (2004); U. Kriebig, M. Vollmer, Optical Properties of Metal Clusters (Spinger, Berlin, 1995); A.C. Templeton, M.P. Wuelfing, R.W. Murray, Acc. Chem. Res. 33, 27 (2000) CrossRefGoogle Scholar
- Portions of these results have been presented in earlier, fragmentary reports: S.-W. Chen et al., Science 280, 2098 (1999); J.T. Khoury, Ph.D. thesis, University of California Los Angeles, 1999; R. Wyrwas, Ph.D. thesis, Georgia Institute of Technology, 2004 Google Scholar
- M.M. Alvarez, J.T. Khoury, T.G. Schaaff, M.N. Shafigullin, I. Vezmar, R.L. Whetten, J. Phys. Chem. B 101, 3706 (1997); R.L. Whetten, J.T. Khoury, M.M. Alvarez, S. Murthy, I. Vezmar, Z.L. Wang, P.W. Stephens, C.L. Cleveland, W.D. Luedtke, U. Landman, Adv. Mater. 8, 428 (1996); T.G. Schaaff, M.N. Shafigullin, J.T. Khoury, I. Vezmar, R.L. Whetten, J. Phys. Chem. B 105, 8785 (2001) CrossRefGoogle Scholar
- C.F. Bohren, D.R. Huffman, Absorption and Scattering of Light by Small Particles (John Wiley and Sons, New York, 1983), p. 117 Google Scholar