Electrically controlled fluorescence in a nematic liquid crystal doped by a chiral fluorophore

We have discovered a strong electric field sensitivity of the fluorescence intensity while studying the diffusion processes of a chiral fluorescent molecule (CFM) in a nematic liquid crystal (NLC) host. The experimental and theoretical study of this phenomenon indicates that the alignment of the CFM along two privileged orientation directions (with asymmetric distribution with respect to the NLC’s optical axis) is in the origin of this phenomenon. As a result, the obtained guest–host system demonstrates noticeable dichroism. Thus, the application of an electric field allows the reorientation of the anisotropy axis of the host, the change of CFM’s absorption (at the wavelength of excitation) and the dynamic electric control of its fluorescence intensity. The study of these phenomena allows also the identification of the angular distribution of guest CFMs suggesting that the elastic energy of orientation of the host molecules might be in the origin of the asymmetric angular distribution of CFM.