Aggregation-induced emission enhancement characteristics of naphthalimide derivatives and their applications in cell imaging

Abstract

Novel naphthalimide derivatives (NIM) with donor-acceptor architecture were successfully constructed and their unique fluorescent properties were investigated. In particular, the fluorescence intensities of 4-methoxystyrene substituted NIM-1 were solvent independent and its quantum yields varied from 0.4 in toluene to 0.52 in MeOH. However, 4-(N,N-diphenylamino) styrene substituted NIM-2 and 4-nitrostyrene substituted NIM-3 exhibited low luminescence in dilute solutions but were efficiently fluorescent under conditions of molecular aggregation. NIM-2 showed strong solid fluorescence with a longer wavelength emission and larger Stokes shift. In addition, NIM-3 showed unexpected blue-green fluorescence due to the formation of fluorescent organic nanoparticles (FONs) under mixed solution. These two cases were ascribed to the aggregation-induced enhanced emission (AIEE) effects and which can also reasonably explain the bright cellular images observed when cells were incubated with NIM-2 and NIM-3. Furthermore, compound NIM-2 can be used to recognize cancer cells owing to its subcellular behaviour.