"Switch-on" fluorescence sensing platform based on porphyrin metal-organic frameworks for rapid and specific...

Zinc ion (Zn²⁺) is a necessary transition metal ion in the human body and plays a vital role in biological systems. Therefore, it is meaningful for rapid, sensitive, and specific detection of Zn²⁺. Herein, a "switch-on" fluorescence sensing platform for the detection of Zn²⁺ was successfully established. In this work, we report an optical nanoprobe with amino functional groups based on porphyrin metal-organic frameworks (PCN-NH₂) through a simple treatment method. The modification of the salicylaldehyde (SA) through the C=N acts as a quencher of PCN-NH₂ and the ligand of Zn²⁺ can effectively inhibit the fluorescence emission of PCN-NH₂. The complex of porphyrin-based metal-organic framework and salicylaldehyde (PCN/SA) acts as the fluorescence sensing probe. The presence of Zn²⁺ results in the new emission peak at 448 nm due to the formation of a complex between Zn²⁺ and SA. The corresponding fluorescence signal changes were used to accurately detect the concentration of Zn²⁺. The fluorescence sensing platform shows advantages, including rapid response, high sensitivity, and excellent specificity with a linear detection range of Zn²⁺ between 0.1 and 250 μM, and a low detection limit (LOD) of 0.07 μM. And the feasibility of the method was verified for the quantification of Zn²⁺ in cell lysate, environmental water, and plasma.