Spherical Silver Nanocrystals Arranged in a Metastable Square Pattern.

The present article demonstrates the development of two-dimensional (2D) assembly of spherical nanocrystals (NCs) in the square arrangement through the delicate balance between repulsive ligand interactions and attractive van der Waals interactions of NCs, respectively, instead of the otherwise stable hexagonal arrangement. The experimental packing efficiency values matched quite well with the theoretically calculated square arrangement patterns. The above fact indicates that the formation of the 2D square arrangement of silver NCs can be explained by introducing the concept of softness to NCs in the hard sphere model.