“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.