Self-Assembly of Au Nanoclusters into Helical Ribbons by Manipulating the Flexibility of Capping Ligands.

Self-assembly is a powerful technology to construct nanomaterials with helical structures. However, using metal nanoclusters (NCs) as the building blocks for the construction of helical architectures is still rarely reported. In this paper, Au NC assembled helical ribbons (Au NCHRs) are successfully constructed by using Au NCs as the building blocks. Effects of heating mode, solvent polarity and ligand length on the self-assembly process of Au NCs are discussed. The results indicate that the lengths of overlapped and nonoverlapped ligands between adjacent Au NCs play the dominated role on adjusting the morphologies of the resulting assemblies. Ligands with appropriate overlap can provide sufficient flexibility for the helical assembly of Au NCs without losing the stability. If the length of the overlapped parts is too long, the assemblies are usually rigid without the helical structure. Instead, the overlength of nonoverlapped ligands will boost the flexibility but damage the structural stability of the assemblies. Since everything in the world is assembled by atoms and molecules, recognizing the self-assembly mechanism of NCs may promote our understanding on the bountiful complexity of life and nature.