A novel triphenylamine-BODIPY dendron: click synthesis, near-infrared emission and a multi-channel chemodosimeter for Hg2+ and Fe3+

Abstract

A novel triphenylamine-BODIPY based Schiff base fluorescent probe (TPA-BODIPY-OH) with an emission in the near-infrared (NIR) region was designed and prepared by click reaction. TPA-BODIPY-OH showed three emission bands at 510 nm, 598 nm and 670 nm, and can detect Fe³⁺ and Hg²⁺ ions with remarkable fluorescence enhancement in THF/H₂O (v/v, 1 : 1, buffered with 10 mM HEPES pH = 7.4) based on the hydrolysis reaction of the –CN bond, and naked eye detection was realized with an obvious color change. The stoichiometry between the probe and ions was deduced from a Job's plot, which is 1 : 3 for TPA-BODIPY-OH/Fe³⁺ and 1 : 2 for TPA-BODIPY-OH/Hg²⁺, respectively. The dissociation constant value was found to be 1.35 × 10⁻¹⁶ M for TPA-BODIPY-OH/Fe³⁺ and 2.06 × 10⁻¹¹ M for TPA-BODIPY-OH/Hg²⁺. The low detection limit was calculated from the titration results with the values of 5.15 × 10⁻⁷ M for TPA-BODIPY-OH/Fe³⁺ and 6.81 × 10⁻⁷ M for TPA-BODIPY-OH/Hg²⁺, respectively. In order to investigate the biological applications of TPA-BODIPY-OH, a living cell imaging experiment was carried out. The results demonstrate that TPA-BODIPY-OH can be successfully applied as a bioimaging agent in living cells. In addition, amino-group-functionalized silica fluorescent nanoparticles (FNPs) encapsulating the TPA-BODIPY-OH dyes were prepared and characterized by transmission electron microscopy. TPA-BODIPY-OH/SiO₂ nanoparticles exhibit good dispersibility, and the quantum yield of FNPs at 657 nm was 42.3%.