"Switch-Off-On" Detection of Fe 3+ and F - Ions Based on Fluorescence Silicon Nanoparticles and Their Application to Food Samples.

An approach to the detection of F - ions in food samples was developed based on a "switch-off-on" fluorescence probe of silicon nanoparticles (SiNPs). The fluorescence of the synthetic SiNPs was gradually quenched in the presence of Fe 3+ ion and slightly recovered with the addition of F - ion owing to the formation of a stable and colorless ferric fluoride. The fluorescence recovery exhibited a good linear relationship (R 2 = 0.9992) as the concentration of F - ion increased from 0 to 100 μmol·L -1 . The detection limit of the established method of F - ion was 0.05 μmol·L -1 . The recovery experiments confirmed the accuracy and reliability of the proposed method. The ultraviolet-visible spectra, fluorescence decays, and zeta potentials evidenced the fluorescence quenching mechanism involving the electron transfer between the SiNPs and Fe 3+ ion, while the fluorescence recovery resulted from the formation of ferric fluoride. Finally, SiNPs were successfully applied to detect F - ions in tap water, Antarctic krill, and Antarctic krill powder.