Cluster size effect observed for gold nanoparticles synthesized by sol-gel technique as studied by X-ray photoelectron spectroscopy

Gold nanoparticles have been synthesized by sol-gel technique. AFM analysis shows the presence of ≤ 12–14 nm and 40–60 nm sized particles for H₂S/not heated and H₂S/heated samples respectively. XPS analysis of H₂S/not heated sample reveals that the core-level Au 4f7/2 B.E. is shifted by +0.3 eV with increase in the FWHM by 0.2 eV relative to the respective bulk values of 84.0 eV and 1.1 eV. The results are interpreted in terms of the changes in the electronic structure due to finite cluster size and creation of +ve charge over the surface of cluster during the photoemission process itself. The electronic structure of Au nanoparticles (or clusters) produced by present sol-gel technique is compared with that of Au clusters deposited by evaporation method described in the literature.