Synthesis and aggregation-induced emission enhancement of naphthalimide-rhodamine dye

•The naphthalimide-rhodamine dye exhibited the significant aggregation-induced emission enhancement.•AIE dye-doped silica nanoparticles were prepared and exhibited good solubility and stability in pure water.•FRET from the naphthalimide to the rhodamine was investigated by Hg2+-induced or H+-induced.

A series of naphthalimide-rhodamine dye L1–4 with the different terminal structures were designed and synthesized. The rhodamine was used as bulky rigid substituent of naphthalimide to enhance the AIE property. All the naphthalimide-rhodamine dye exhibited the significant aggregation-induced emission enhancement. The strong fluorescence emissions in solid state were observed with emission peaks ranging from 549 to 608 nm. In high fW mixture solution, the fluorescence intensity enhanced with the increase of water content, which can be attributed to two types of aggregation-induced morphology. The AIE dye-doped silica nanoparticles (Si-NPs) were prepared and exhibited good solubility in pure water. In addition, dye L1 and L2 exhibited the selective recognition toward Hg2+ ions and were successfully applied to the bioimages in living cells. The intramolecular fluorescence resonance energy transfer mechanism from the naphthalimide moiety to the rhodamine moiety was investigated.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideA series of naphthalimide-rhodamine dye L1–4 with the different terminal structures were designed and synthesized. All the naphthalimide-rhodamine dye exhibited the significant aggregation-induced emission enhancement. In addition, the AIE dye-doped silica nanoparticles were prepared and the naphthalimide-rhodamine dye was successfully applied to the bioimages in living cells.