Design and Characterization of Novel Naphthalimide Fluorescent Probe for H₂S Detection in Human Serum

In this work, a novel fluorescent probe (compound 2) based on the Intramolecular charge transfer (ICT) mechanism was designed and successfully applied to determine H₂S in human serum. Fluorophore 1,8-naphthalimide was chosen, while the azide group was the recognition group for H₂S determination. By introducing p-toluidine moiety on the imide part of the molecule, a donor-acceptor (D-A) conjugated system was formed. Prepared compound 2 was characterized using ¹H, ¹³C NMR spectroscopy, and elemental analysis. Fluorescence spectra measurements were carried out, and several influences on fluorescence intensity were investigated, including pH, time dependence, selective response, and influence of H₂S concentration. Conducted experiments, including the calculated detection limit of the prepared fluorescent probe, which was found to be 0.085 µmol·L^- 1, showing that compound 2 could be applied for H₂S detection in human serum and could detect low micromolar concentrations of H₂S. Finally, compound 2 was successfully applied to detect H₂S in a human serum sample, whereby the concentration of H₂S was 17.2 µmol·L^- 1. The accuracy of the H₂S determination was confirmed with the standard addition method.