Controlling Supramolecular Self-Assembly and Nanostructures: A Comparative Study in the Solution Phase and at the Air–Water Interface

Abstract

The controlled molecular assembly of small units is a pivotal technology for the development of smart organic materials, serving as a fundamental approach to fabricating nanodevices in the fields of electronics, optoelectronics, and biological sciences. Herein, we have demonstrated how to control the self-assembly behavior of chiral amphiphilic naphthalene diimide derivatives (NDI-L and NDI-D) through different self-assembling methods such as in the solution phase and at the air–water (A-W) interface. NDI-L and NDI-D were self-assembled into nanoparticles with strong mirror-imaged circular dichroism (CD) signals for NDI-L and NDI-D, respectively, in the solution phase (aqueous solution). Intriguingly, multilayers of these systems fabricated using the Langmuir–Blodgett methods lack CD signals. We observed two-dimensional (2D) aggregates with irregular boundaries for both NDI-L and NDI-D having two phases (L2 and L2’ which differ in the tilt) of different elasticities when assembled at the air–water (A-W) interface. This phenomenon demonstrated that NDI chromophores organized themselves differently when they self-assembled in solution compared to when they assembled at the A-W interface. Controlling self-assembly behavior through different techniques will open up an avenue for researchers to develop advanced supramolecular functional materials for potential applications in various fields ranging from material science to biomedicine.