Bright and stable Cy3-encapsulated fluorescent silica nanoparticles with a large Stokes shift

Traditional organic fluorophores, like cyanine dyes, suffer from their poor stability and weak brightness of individual molecule. In this work, a novel cyanine dye with a large Stokes shift (∼75 nm) was encapsulated inside silica nanoparticles. The obtained small fluorescent silica nanoparticle (FSNP) exhibits more than ten times brightness than the free dye. The enhanced fluorescence brightness was assigned to the less homo Förster resonance energy transfer (HFRET) between multiple fluorophores, which was confirmed by the longer fluorescence lifetime of FSNP with a large Stokes shift than that with a normal Stokes shift. The FSNP’s photostability is much better than organic fluorophores and comparable with that of Quantum Dots. When used in bioimaging, the FSNP remained a stable fluorescence signal, while the control free dye faded within 12 h.

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► A new cyanine dye with a large Stokes shift (74 nm) was synthesized.
► The dye was encapsulated inside a silica nanoparticle in a core-shell format.
► The obtained nanoparticle exhibits brighter fluorescence than the free dye.
► The enhanced fluorescence brightness was assigned to the less homo-FRET.
► Better photostability and biostability are achieved.