Self-assembled monolayers (SAMs) of organic ligands on gold have attracted lots of research interest in recent years. The protecting ligands are given many functions in addition to their basic role as surface stabilizers, which in turn generate significant applications in the fields of electronics, sensing, drug delivery and nanotechnology. The classical coating ligands are sulfur-containing thiols, which has been widely studied and the Au-S interface structure has been well understood and characterized. Besides thiols, a lot of alternative ligands have been explored as stabilizers for gold, such as phosphines, amines, aryl radicals, as well as the recently discovered alkynl groups and N-heterocyclic carbenes (NHCs), and new interfacial structures and functionalities have been reported. The ultimate utility of SAMs-derived gold nanosystems will be critically dependent on their stability. To our knowledge, however, there has been no systematic comparison between these ligands in terms of their bonding strength to gold. In this work, using Au(111) surface as the model system, we performed density functional theory (DFT) calculations to examine the bound stability of different classes of anchoring groups to the perfect and “adatom” Au(111) surface. Our results indicated that NHCs with bulkier substitutes and the terminal alkynes (e.g., phenylacetylene) form stronger bonds to gold as compared to thiols, phosphines or aryl radicals, while amines form the weakest bonding. The theoretical picture provided here will give enlightening insight for experimental peers in the future selection of the promising groups for any given application.

Comparative studies on ligand binding stability on Au(111) surface

251st National Meeting (2016)

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