1：Experimental Design and Method Selection:

The study involved designing a chemosensor L3 based on 1,8-naphthalimide with a thiol group for selective Hg2+ detection. Methods included synthesis, spectroscopic characterization (UV-Vis, fluorescence), titration experiments, DFT calculations, and real sample analysis.

2：Sample Selection and Data Sources:

Stock solutions of metal ions (perchlorates) were prepared. Water samples from Ganga canal and drain water were collected and analyzed.

3：List of Experimental Equipment and Materials:

Instruments used include FTIR spectrometer (Bruker Alpha), NMR spectrometer (Bruker DPX 500 MHz), spectrophotometer (Specord S600 PC), fluorometer (Horiba RF-5301PC), melting point apparatus (Optimelt), fluorescence lifetime system (HORIBA Jobin Yvon Fluorocube), and ICP-MS. Reagents included 1,8-naphthalicanhydride, 2-aminobenzenethiol, triethylamine, acetonitrile, deionized water, and metal perchlorates.

4：Experimental Procedures and Operational Workflow:

Synthesis of L3 via amidation reaction. Absorbance and fluorescence measurements were performed by titrating L3 with Hg2+ and other metal ions in CH3CN:H2O (1:1 v/v, pH 7.0 HEPES buffer). Job's plot, Benesi-Hildebrand plot, pH dependence, reversibility with KI, and real sample analysis were conducted.

5：0 HEPES buffer). Job's plot, Benesi-Hildebrand plot, pH dependence, reversibility with KI, and real sample analysis were conducted. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using linear regression for detection limit calculation, DFT for theoretical insights, and statistical methods for real sample recovery.