We report a study of the structure and electronic properties of a series of thiol-capped Au nanoparticles (NP) of nominal sizes of 1.6, 2.4, and 4.0 nm. Transmission electron microscopy, x-ray powder diffraction, x-ray absorption fine structure, and x-ray photoemission spectroscopy have been used to investigate the size-dependent systematics of lattice contraction and charge redistribution of these NPs. It is found that the lattice contracts and the $d$ charge at the Au atom site depletes relative to bulk Au as the size of the NP decreases. The implication of these observations is discussed in terms of the interplay of quantum-size and surface effect.

• Received 3 February 2003

DOI:https://doi.org/10.1103/PhysRevLett.90.245502