A Novel Fluorescent Probe AP for Highly Selective and Sensitive Detection of Hg2+ and Its Application in Environmental Monitoring

Mercury is a highly toxic heavy metal that poses serious threats to human health and environmental safety, highlighting the critical importance of accurate Hg2+ detection. In this study, a novel fluorescent probe AP was synthesized by conjugating fluorescein, serving as the luminescent group, with pyridine-2-carboxaldehyde to enable selective Hg2+ detection. Hg2+ binds to AP in a 1:2 stoichiometric ratio, inducing the opening of the spiro-lactam ring and resulting in a significant fluorescence enhancement. The probe exhibited excellent selectivity and sensitivity toward Hg2+. A strong linear correlation was observed between its fluorescence intensity and Hg2+ concentration (R2 = 0.99952), with a detection limit of as low as 9.75 × 10−8 mol/L. The average recoveries of Hg2+ across various water matrices ranged from 95.23% to 103.40%, with relative standard deviations (RSDs) below 3.07%. These results indicate that the probe performs effectively in real water-sample testing.