A novel fluorimetric sensing strategy for highly sensitive detection of phytic acid and hydrogen peroxide

In this paper, we developed a sensitive sensor for phytic acid (PA) and hydrogen peroxide (H₂O₂) detection based on glutathione-functionalized graphene quantum dots (GQDs@GSH). The fluorescence of GQDs@GSH was found to be effectively quenched by Fe³⁺ ions via photo-induced electron transfer (PET) process. Upon the addition of PA to GQDs@GSH/Fe³⁺ system, the fluorescence of GQDs@GSH was significantly restored due to the strong chelating and reducing ability of PA, Fe³⁺ ions could be reduced to Fe²⁺ ions by PA and formed PA/Fe²⁺ complex. Therefore, the "off-on" fluorescence method was constructed to detect PA by using GQDs@GSH/Fe³⁺ as a fluorescent probe. Furthermore, the method can be used for the detection of H₂O₂. H₂O₂ can destroy the chelate structure of PA/Fe²⁺, release Fe²⁺ ions and oxidize Fe²⁺ ions to produce Fe³⁺ ions, leading to the fluorescence quenching of GQDs@GSH again. Under optimal conditions, the fluorescence sensing platform showed good linear relationship between the relative fluorescence intensity I/I₀ and the concentration of PA and H₂O₂ in the range of 0.05-3 μmol L^-1 and 0.5-10 μmol L^-1, respectively. The detection limits of PA and H₂O₂ were 14 nmol L^-1 and 0.134 μmol L^-1, respectively. Furthermore, the fluorescence assay method was also applied in real sample analysis and satisfactory results were obtained.