Study of the Synthesis and Application of a Fluorescence‐Enhanced Mg2+ Probe

Abstract A Schiff base fluorescent probe compound H 2 L (N′‐(4‐bromo‐2‐hydroxy‐benzylidene)‐3‐hydroxy‐2naphthohydrazide) was synthesized using 3‐hydroxy‐2‐naphthoic acid hydrazide as raw material. The structure of H 2 L was characterized by NMR, IR, MS, and XRD methods. The fluorescence performance of H 2 L was studied by UV and FS. The results show that in 1 : 4 water system /DMSO solution (water system: 20 % triethanolamine:0.1 mol/L L‐cysteamine acid=1 : 1), H 2 L can be used to quickly identify Mg 2+ with an obvious fluorescence enhancement and redshift. A color change “light green→bright yellow” can be clearly observed with the naked eye. The Mg 2+ concentration shows a good linear relationship in the range of 0–1.0×10 −5 mol/L, with a detection limit of 1.77×10 −7 mol/L with good stability and reversibility. The response mechanism was explored through Job's curve, NMR titration and MS, which showed that Mg 2+ can form a 1 : 1 complex with H 2 L . A gel (SAL) was prepared by doping H 2 L into sodium alginate (SA). SAL was found to show good adsorption properties for Mg 2+ and can be easily distinguished by the naked eye under ultraviolet light. The microscopic morphology and composition of SAL before and after Mg 2+ adsorption were analyzed by SEM‐EDS. H 2 L can be used for the qualitative detection of Mg 2+ in actual water samples without being affected by other common metal ions, and has potential application value in the field of environmental detection.