Interfacial energy consideration in the organization of a quantum dot–lipid mixed system

We propose a theoretical model for a quantum dot (QD)–lipid mixed system based on a simple geometrical assumption for a single-component lipid (DOPC) monolayer deformation profile. In this system, there are two possible states: a quantum dot–liposome complex (QLC) state where QDs are incorporated into the lipid bilayer of the liposome, and a quantum dot–micelle complex (QMC) state where an individual QD is covered by a lipid monolayer. In this model, the elastic deformation energy of the QLC is smaller (larger) than that of the QMC for the QD size smaller (larger) than a certain critical size. Therefore, the QLC is a more stable state than the QMC for the QD size smaller than a certain critical size. The prediction shown in this model is very consistent with our recent experimental results. To our knowledge, this is the first theoretical model that predicts the size dependence of the stability of the QD in the lipid bilayer.