We found that flavonol- 2’-sulfonate (Flav-s) is robustly adsorbed on the surface of ZrO2 nanoparticle (29 nm in diameter) and the nanocomposite show strong fluorescence that is distinctively different from those of free fFlav-s. A blue fluorescence test strip for fluoride ion was also demonstrated by Flav-s/ZrO2 nanocomposite onto a membrane filter. The Flav-s itself shows weak fluorescence in powder form, whereas surface-adsorbed flavonoids on ZrO2nanoparticles in aqueous solutions show intense and blue shift fluorescence. The complex formation reaction between Flav-s and ZrO2 in aqueous solutions was investigated via equilibrium dialysis method and the fluorescence quantum yield of the resulting blue fluorescent nanocomposite was measured with reference to quinine sulfate. The stability constant of Flav-s/ZrO2 was estimated to be 9.27 ×105 M–1 at pH 3, which is larger than those of other bidentate ligands/metal oxide composites. The extremely strong blue fluorescence of Flav-s/ZrO2 was expressed to be Φf 0.67 (λex 370 nm,λem 450 nm) as opposed to week green fluorescence of flav-s Φf 0.30 (λex 326 nm, λem 520 nm) , the peculiar resonance structure is expected and shown in Figure 1. The Flav-s/ZrO2 test paper was fabricated by simple filtration of the Flav-s/ZrO2 dispersion though a membrane filter and the ligand exchange reaction of Flav-s to F– in aqueous media was explored by the decrease of the fluorescence of Flav-s/ZrO2 test strip. The detection range of F– was estimated to be from the 3σdetection limit of 0.13 ppb (n = 4) to 10 ppm as shown in Figure 2.

Distinctive fluorescence of water-soluble flavonol induced by the surface bonding on ZrO2nanoparticle and its application to a test strip for fluoride ion detection

2019 Spring National Meeting

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