An Effective Method for the Preparation of Stable LC Composites with High Concentration of Quantum Dots

Abstract

Cholesteric liquid crystals doped with QDs present a special interest because the photonic bandgap structure of cholesteric media when combined with emission properties of QDs provides the opportunity to realize a variety of specifi c photooptical properties. Cholesteric mesophase has a 1D photonic bandgap structure, which stands for its unique optical properties such as Bragg selective light refl ection, huge optical rotation, and so on. [ 20 ] In several recent papers, the optical and photophysical properties of the cholesteric low-molar-mass and polymer liquid crystalline (LC) materials doped with QDs were demonstrated. [ 16‐18 ] For example, in recent publication, [ 16 ] the modulation of recombination lifetimes of CdSe/ZnS QDs (0.01‐0.02 wt%) dispersed in cholesteric low-molar-mass liquid crystal and time-resolved emission from QD ensembles in LC matrices with different alignment were investigated. The difference in decay time characteristics of QD’s emission depending on planar or homeotropic alignment was revealed in the case of overlapping of emission and photonic bandgap peaks. It was shown that coupling between the excitonic and the photonic cavity modes leads to the enhancement and modulation of spontaneous emission. In the papers [ 18,19 ] we have described the novel types of cholesteric QDs-doped materials with photo- and electro-tunable fl uorescence. The possibility of manipulation of fl intensity and degree of circular polarization (dissymmetry factor) was demonstrated for the fi rst time. Despite a great progress in the fi eld of the QD‐LC composites, the introduction of large concentration of QDs into liquid crystal media is still a challenging task. The most successful achievement in the area was published recently. [ 15 ] The authors of this work have offered an approach based on the surface