Modifying the Atomic and Electronic Structures of Gold Nanocrystals via Changing the Chain Length of n-Alkanethiol Ligands

Abstract

The interfacial atomic and electronic structures of ligand-protected nanomaterials are vital factors but are inadequately known. Here, we demonstrate that the adsorption geometry, as well as the electronic structures of Au–S interface, can be tailored via varying the hydrocarbon “tail” lengths of n-alkanethiol ligands. Fully n-alkanethiols (n = 3, 8, and 12) capped Au nanocrystals of 3.0 nm were characterized in solution by X-ray absorption fine structure at the Au L3-edge. With increasing alkyl length, it is found that the headgroup S atom occupies the nanocrystals surface sites with gradually higher coordinations, along with the progressively shortened Au–S bond length. As a result, the strongest Au–S interactions coming from the longest n-alkanethiols capping lead to the most significant d charge transfer from the surface Au layer to the S atoms.