“Switch-Off-On” Detection of Fe3+ 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 Fe3+ 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 (R2 = 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 Fe3+ 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.