Design and Characterization of Novel Naphthalimide Fluorescent Probe for HS 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 HS in human serum. Fluorophore 1,8-naphthalimide was chosen, while the azide group was the recognition group for HS 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 H, C 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 HS concentration. Conducted experiments, including the calculated detection limit of the prepared fluorescent probe, which was found to be 0.085 µmol·L, showing that compound 2 could be applied for HS detection in human serum and could detect low micromolar concentrations of HS. Finally, compound 2 was successfully applied to detect HS in a human serum sample, whereby the concentration of HS was 17.2 µmol·L. The accuracy of the HS determination was confirmed with the standard addition method.