Fig. 2: Dynamic FRET systems constructed in the helical superstructures of CLCs.
a Fluorescence spectrum of (S)-CNB in the 5CB host (3.0 wt%, λex = 365 nm); the inset shows the fluorescent photograph of (S)-CNB. Fluorescence spectra of b DG (1.0 wt%, λex = 450 nm) and c DR (1.0 wt%, λex = 500 nm) in the 5CB host before and after UV irradiation (1.0 mW/cm2); the insets show the fluorescent photographs (black lines for open-isomers and green/red lines for closed-isomers). d Normalized absorption and normalized fluorescence spectra of (S)-CNB, closed-DG, and closed-DR (blue, green, and red dotted lines for the absorption of (S)-CNB, closed-DG, and closed-DR, blue, green, and red solid lines for the fluorescence of (S)-CNB, closed-DG, and closed-DR). Fluorescence and mirror CPL spectra of e LC-D (CNB:DG = 3.0 wt% :1.5 wt%, λex = 365 nm) and f LC-T (CNB:DG: DR = 3.0 wt% :1.5 wt% :1 wt%, λex = 365 nm) before and after UV irradiation (1.0 mW/cm2); the insets show the fluorescent photographs (dotted lines for (R)-LC systems and solid lines for (S)-LC systems). g Chemical structures of chiral donor (S)-CNB and achiral acceptors DG and DR. h Schematic illustration of phototunable CPL and fluorescnece in LC-D and LC-T through dynamic FRET processes. Fluorescence decay profile of (S)-CNB in i (S)-LC-D and j (S)-LC-T before and after UV irradiation (λex = 365 nm, monitored at 434 nm) (blue squares for initial states of (S)-LC-D and (S)-LC-T, green circle for PSS365 of (S)-LC-D, red rhombus for PSS365 of (S)-LC-T). k Schematic diagram of stepwise FRET from CNB to closed-DR in the LC-T system in which closed-DG serves as the intermediate bridge.
