Lamellar Nanosheets of Water-Insoluble Amphiphiles via Aqueous Solution and Air/Liquid Interface Self-Assembly

Two-dimensional (2D) lamellar nanostructures have attracted much interest due to their unique structure and properties. Various fabrication methods have been developed in recent years, including solution self-assembly, exfoliation, and Langmuir monolayer and Langmuir-Blodgett (LB) deposition. In this work, two kinds of facile methods were applied to fabricate lamellar structures of amphiphilic molecules, such as 10,12-pentacosadiynoic acid (PCDA). In method I, the amphiphilic molecules were introduced into aqueous solutions with dimethylformamide (DMF), a solvent miscible with water, through a mass transfer process across a planar liquid/liquid interface; in method II, the DMF solution of the amphiphilic molecules was added directly onto the aqueous solution surface. With the spread and diffusion of DMF, nanosheets with lamellar structures formed in the aqueous solution and at the air/liquid interface, respectively. It is very interesting that the nanosheets obtained through these two methods consist of an even number and odd number of PCDA monolayers, respectively, reflecting different fabrication mechanisms. Method I provides an approach to gently mix organic solutions with aqueous solutions, while method II can be regarded as an extension of the Langmuir monolayer technique, which combines the interfacial assembly with that in solution. These methods have been extended to a series of amphiphilic molecules, and ordered layered structures have been obtained successfully.