Smartphone-based ratiometric fluorescent definable system for phosphate by merged metal-organic frameworks

Phosphate plays an important role in a wide range of chemical and biological processes, so the development of a new phosphate optical sensor with high sensitivity, specificity and visual recognition function has important practical significance. Herein, a ratiometric fluorescent (RF) probe and a smartphone-integrated colorimetric test paper sensing platform for assay phosphate was fabricated using hybrid fluorescent UiO-66-NH₂ and Eu³⁺@MOF-808 metal-organic frameworks. After continuous addition of phosphate, the blue fluorescence emission of UiO-66-NH₂ and the red emission of Eu³⁺@MOF-808 were regularly enhanced and quenched respectively, and the fluorescence response of the detection platform to phosphate exhibited a clear color change process (red → pink → blue). More importantly, the probe solution and test paper of the integrated smartphone are converted to digital values through RGB channels and successfully used to visualize semi-quantitative recognition of phosphate. In addition, an RF probe and a smartphone integrated fluorescent test paper were developed separately to devise logic gate devices for detecting phosphate. The multifunctional ratio sensing platform integrated by the smartphone furnishes a new strategy and broad prospects for the intelligent online identification of important targets in biological samples and environmental samples.