Self-Assembly of CdSe Nanoplatelets into Stacks of Controlled Size Induced by Ligand Exchange

In this paper we present a simple method for the preparation of highly stable colloidal solutions of individual nanoplatelets (NPls) with increased fluorescence quantum yield and a versatile procedure of NPls self-assembly into stacks of controlled size. Dynamic light scattering technique has been demonstrated to be simple and accurate method for in situ studies of the growth kinetics of NPls aggregates. The self-assembly method introduced in this work is based on the exchange of ligands on the surface of CdSe nanoplatelets. Hexadecylphosphonic acid allows control of the average size (length) of NPls stacks in a broad range by varying its concentration and reaction time. The main mechanism governing controlled formation of NPls stacks is based on strong van der Waals interaction between rigid brushes of alkyl chains on the surface of neighboring NPls. The interaction strength and, consequently, the length and colloidal stability of stacks have been shown to be dependent on type and concentration of different ligands