Ratiometric fluorescent sensing of phosphate ion in environmental water samples using flavin mononucleotide-functionalized Fe3O4 particles

作者：Xu, Fang^*; Leng, Wei; Lu, Qinwei; Li, Kunpeng; Zhang, Yukuai; Liu, Jingyu; Xu, Liqiang; Sheng, Guoping

来源：Science of the Total Environment, 2023, 857: 159249.

DOI：10.1016/j.scitotenv.2022.159249

• Phosphate ion
• Flavin mononucleotide
• Fluorescent sensing
• Water -quality monitoring
• Vitamin B 2

Phosphate ion (POq-) serves as an important nutrient carrier to support the growth of aquatic animals and plants in aquatic systems. However, excess concentrations of POq- are the key factor responsible for eutrophication, resulting in rapid deterioration of water quality. Therefore, accurate determination of POq- is of great significance in water quality and security. In this study, flavin mononucleotide (FMN), an intracellular form of vitamin B2, was used as fluorophore. A novel "off-on" fluorescent sensing platform (FMN@Fe3O4) was fabricated for selective and sensitive detection of POq-, and showed excellent fluorescence response and good selectivity for POq- detection. With the addition of POq-, the fluorescence intensity restored is proportional to POq- concentration in the quantification range of 50 nM-0.75 mu M with a limit of detection as low as 20 nM (0.62 mu g.L-1, calculated by P element). An adsorption/ desorption sensing mechanism via an in-depth analysis of the interfacial interaction between POq- and FMN@Fe3O4 is proposed. FMN is first adsorbed by its terminal phosphate group on Fe3O4 particles to quench fluorescence. Free POq- replaces the adsorbed FMN and restores the quenched fluorescence to achieve the aim of POq- detection. In addition, this sensing system has been successfully validated in real water sample analysis and all reagents involved are nontoxic, environmentally benign, and easily-available. Therefore, this assay has great applicability in water quality monitoring.