Fluorescein@NH2-UiO-66 Probe for Ratiometric Fluorescence Sensing of Trace Phosphate in Water

Phosphate pollution leads to deterioration in water quality, posing a serious threat to human health. Therefore, it is important to develop a highly selective and sensitive fluorescent probe for phosphate detection. Here, we report a novel ratiometric fluorescent probe, Fluorescein@NH2-UiO-66 (denoted as Flu@NH2-UiO-66), for the trace detection of phosphate in water. Specifically, during the in-situ solvothermal synthesis of Flu@NH2-UiO-66, fluorescein molecules were encapsulated into the cavities of the metal-organic framework. Furthermore, the encapsulation amount of fluorescein was controlled by adjusting the acidity of the system. The Flu@NH2-UiO-66 (60 H+) sample, prepared with a 60:1 molar ratio of acetic acid to the metal center exhibited distinct dual fluorescence signal peaks. The probe showed a highly selective fluorescence response to phosphate. Within a range of 0-20 μM phosphate concentration, the probe demonstrated excellent linear detection capability with a detection limit of 0.37 μM. Moreover, the mechanism of fluorescence enhancement can be attributed to the addition of phosphate, which greatly increases the UV absorbance of the probe. This study developed a novel ratiometric fluorescent probe capable of rapid, sensitive, and stable detection of trace phosphate, which is of great significance for environmental management.