9-Aryl-1,2-dihydropyrrolo[3,4-b]indolizin-3-one (Seoul-Fluor) as a smart platform for colorful ratiometric fluorescent pH sensors.

9-Aryl-1,2-dihydropyrrolo[3,4-b]indolizin-3-one (Seoul-Fluor) as a smart platform for colorful ratiometric fluorescent pH sensors.