Perylene-3,4,9,10-tetracarboxylic tetraester-based fluorescent PET probes with aniline receptors attached either at the peri- or the bay-positions have been synthesized. By attaching aniline receptors at the bay position, pH-sensitive "light-up" probes, with fluorescence quantum yields ΦF > 0.75 and fluorescent enhancements FE > 500 in ethanol, have been obtained.