A Low-Symmetry Cubic Mesophase of Dendronized CdS Nanoparticles and Their Structure-Dependent Photoluminescence

A liquid crystal (LC) phase with P2₁3 symmetry, the lowest so far in a cubic LC, was obtained in a system of CdS quantum dots (QDs) modified with a two-layer corona of aliphatic thiols (inner) and LC aromatic dendrons (outer). We propose that the unusual low symmetry of this cubic mesophase is a result of the multi-layered corona, which prefers to adopt an anisotropic radial profile because of the combination of long and short “bristles.” The anisotropic distribution of dendrons (long bristles) in the P2₁3 phase is thought to facilitate π-π interaction among the aromatic moieties. The interaction gives rise to non-radiative exciton energy-transfer pathways that induce photoluminescence quenching of the CdS QDs. This is believed to be the first example of structure-dependent emission-quenching behavior.