Inter-atomic distance contraction in thiol-passivated gold nanoparticles

Size-dependent inter-atomic distance contraction was investigated by Extend ed X-ray Absorption Fine Structure in thiol-capped gold nanoparticles, A sl ight nearest-neighbor distance reduction was observed as a function of part icle diameter (2-4 nm range) but, for all samples, it was less than 1%. Thi s value contrasts with the larger effect expected and found in other system s, especially for the smallest particles (2 nm) where it is twice as small. Our analysis also points out a short metal-ligand bond, suggesting a rathe r strong surface interaction. We interpreted these results as a passivant e ffect where the metal-ligand interaction partially compensates the expected lattice contraction. (C) 2000 Elsevier Science B.V. All rights reserved.