“…Additionally, we studied the fluorescence behavior of 4 in different water-glycerol fractions and observed fluorescence enhancement by increasing the solvent viscosity (Figure 5b). Several twisted intramolecular charge transfer (TICT)-based fluorogenic probes for various targets, such as biothiol, reactive oxygen species, and HSA, demonstrated the TICT characteristics of the probe through theoretical calculations, showing the charge separation in the HOMO-LUMO transition, and by experimental confirmation of the solvent effect on fluorescence [47,48,49,50,51,52,53]. As in previous reports, these results, including the ICT character and viscosity-dependence of the fluorescence intensity of 4, showed the typical phenomena of a TICT-based fluorogenic probe.…”