Ratiometric fluorescent sensing for phosphate based on Eu/Ce/UiO-66-(COOH)2 nanoprobe

The sensing of phosphate anion (PO43−) is an important subject for human health and environmental monitoring. Herein, a unique ratiometric fluorescent nanoprobe based on postsynthetic modification of metal-organic frameworks (MOF) UiO-66-(COOH)2 with Eu3+ and Ce3+ ions toward PO43− was proposed (designated as Eu/Ce/Uio-66-(COOH)2). The Eu/Ce/Uio-66-(COOH)2 nanoprobe exhibits three emission peaks at 377 nm, 509 nm, and 621 nm with the single excitation wavelength at 250 nm, respectively. The strong coordinating interaction between Ce3+ and O atoms in the PO43− group can result in the fluorescence quenching at 377 nm, while the fluorescence of 621 nm almost remains unchanged. Such a useful phenomenon is exploited for the construction of a ratiometric fluorescence platform for the detection of PO43−. The assay exhibited a good linear response in the 0.3–20 μM concentration range with the detection limit of 0.247 μM. In addition, this ratiometric fluorescent sensing method not only can be applied to read out PO43− concentration in real water samples, but also shows higher sensitivity, easier preparation and sensing procedures than other detection strategies.