[Spectroscopic studies on electrostatically self-assembled gold nanoparticulate thin films].

Colloidal gold was prepared by citrate-induced reduction of hydrogen tetrachloroaurate. Gold nanoparticulate thin films were built up using the electrostatic self-assembly technique and characterized by different spectroscopes. The UV-Vis absorbance spectrum indicated that the gold colloid was a monodisperse suspension. The calculation using the Scherrer's equation on base of the X-ray diffraction spectrum indicated that the average size of the gold particles assembled on the substrates was about 21 nm. The X-ray photoelectron spectra showed that the reduction of hydrogen tetrachloroaurate was almost complete and that the gold was present in the thin films largely as Au zero. The X-ray photoelectron spectra also showed that the gold particles were attracted and fixed onto the PDDA-modified substrates by electrostatic forces. The UV-Vis absorbance spectra and the surface enhanced Raman scattering spectra indicated that, arising from the interparticle coupling, the gold nanoparticulate thin films displayed strong collective plasma resonance absorption and sur faced enhanced Raman scattering effect.