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

Zinc ion (Zn) 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 Zn. Herein, a "switch-on" fluorescence sensing platform for the detection of Zn was successfully established. In this work, we report an optical nanoprobe with amino functional groups based on porphyrin metal-organic frameworks (PCN-NH) through a simple treatment method. The modification of the salicylaldehyde (SA) through the C=N acts as a quencher of PCN-NH and the ligand of Zn can effectively inhibit the fluorescence emission of PCN-NH. The complex of porphyrin-based metal-organic framework and salicylaldehyde (PCN/SA) acts as the fluorescence sensing probe. The presence of Zn results in the new emission peak at 448 nm due to the formation of a complex between Zn and SA. The corresponding fluorescence signal changes were used to accurately detect the concentration of Zn. The fluorescence sensing platform shows advantages, including rapid response, high sensitivity, and excellent specificity with a linear detection range of Zn 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 Zn in cell lysate, environmental water, and plasma.