Fig. 1. PL modulation of CQD and DAE. (a) Schematic illustration and (b) photographs of PL modulation of the CQDs and DAEs in the on and off states. (c) Isomerization of o-DAE and c-DAE.

Fig. 2. Characterization of CQDs. (a) TEM image of CQDs. (b) FTIR spectrum of CQDs.

Fig. 3. Absorption and PL spectra of CQDs and DAEs. (a) Absorption and PL spectra of CQDs (excited at 440 nm) in ethanol. (b) Absorption spectra of 50 µM DAE in ethanol. DAE was irradiated by 310 and 515 nm lights to the respective photostationary states.

Fig. 4. Light modulation of the absorption and PL spectra of CQDs mixed with DAEs. (a) Absorption spectra and (b) PL spectra of CQDs mixed with DAEs. (c) PL modulation switching over 20 cycles. DAE was irradiated by 310 and 515 nm lights to the respective photostationary states.

Fig. 5. PL and quenching behavior of CQDs and DAEs. (a) PL spectra of CQDs and (b) PL lifetime of the CQDs with c-DAEs (concentrations of 0, 10, 25, 50, and 100 µM in ethanol).

Fig. 6. Stern–Volmer plots of the mixture of CQDs and DAEs and geometrical structures of o-DAE and c-DAE. (a) Stern–Volmer plots for PL intensity of CQDs in 10 mm cuvette at 0°C and 70°C. (b) Side-views of the geometrical structures of o-DAE and c-DAE.