Detection of Silver and Mercury Ions Using Naphthalimide-Based Fluorescent Probe.

A multifunctional fluorescent probe P based on a naphthalimide derivative for the detection of Ag⁺ and Hg²⁺ through a dual-signal was designed and characterized. P exhibited a large Stokes shift (107 nm), high selectivity, good sensitivity, and fast response time. By adjusting the testing medium and the order of reagent addition, multifunctional detection with P was achieved. The addition of Ag⁺ or Hg²⁺ to P solution in either ethanol or an ethanol-water mixture resulted in a significant quenching of fluorescence emission at 537 nm and caused a decrease in the absorbance at 440 nm accompanied by the appearance of a new absorption peak at around 340 nm, and there was an obvious color change from yellow to colorless. In contrast, the addition of other common metal ions and anions did not produce substantial spectral or color changes. The detection limit of probe P for Ag⁺ and Hg²⁺ was calculated to be 0.33 μM. The sensing mechanism was proposed and validated through MS and ¹H NMR spectrometry methods. Additionally, P demonstrated the capability to recognize Ag⁺ and Hg²⁺ in living cells with satisfactory results.