Aggregation-induced emission enhancement and cell imaging of a novel (carbazol-N-yl)triphenylamine–BODIPY

Abstract

A novel red aggregation-induced emission enhancement (AIEE) chromophore named BCPA–BODIPY was synthesized based on the construction units 4-N,N-bis[4-(3,6-di-tert-butylcarbazol-9-yl)phenyl]amino-benzaldehyde (BCPA) and fluorogen dipyrromethene boron difluoride (BODIPY). BCPA exhibits bright blue fluorescence (λ_em = 485 nm) in the solid state while BCPA–BODIPY emits bright red fluorescence in the solid state with a maximum emission wavelength at 633 nm. An obvious bathochromic shift from 485 nm to 633 nm was observed by modification of the BODIPY moiety on BCPA. Its fluorescence spectrum indicates that BCPA–BODIPY is a bimodal structure centred at 520 nm and 656 nm in THF solution; there was almost no fluorescence in pure THF. However, the intensities (>600 nm) increased obviously with much higher water fractions, demonstrating typical red fluorescence enhancement. Meanwhile, BCPA–BODIPY became a strong emitter in DMF and high viscosity glycerol mixtures which indicates that the intramolecular vibration and rotation of BCPA–BODIPY is considerably restricted in nanoaggregates formed in glycerol, thus leading to significant fluorescence enhancement. Besides, dye-loaded nanoparticles encapsulating BCPA–BODIPY maintain and further reinforce the AIEE effect and achieve higher water solubility. The pure dye was applied in cell imaging and showed a good uptake by MCF-7 cells which suggests it to be promising in biosensor applications.