1：Experimental Design and Method Selection:

The study involved designing fluorescence-enhanced probes based on 4-hydroxy-1,8-naphthalimide with 2,4-dinitrophenyl ether as the H2S response site, utilizing photoinduced electron transfer (PET) mechanism. Synthetic routes followed references [27-30], and mechanisms were investigated using time-dependent hybrid density functional theory (TDDFT).

2：Sample Selection and Data Sources:

Probes NTE-1 and NTE-2 were synthesized and tested. H2S was replaced by sodium sulfide (Na2S) in neutral buffer solutions. Water samples (tap water and rainwater) were used for practical application tests.

3：List of Experimental Equipment and Materials:

Instruments included Bruker Avance III for NMR, Bruker microOTOF-Q II for HRMS, X-4A melting point meter, UV-4802 spectrophotometer, F-2500 fluorescence spectrometer, and Gaussian 09 for calculations. Materials included silica gel, chemical reagents (e.g., 4-bromo-1,8-naphthalene anhydride, 2,4-dinitrobromobenzene), and solvents (e.g., DMSO, DMF).

4：Experimental Procedures and Operational Workflow:

Synthesis involved refluxing, filtration, column chromatography, and purification. Fluorescence tests were conducted by preparing probe solutions in PBS/EtOH, adding Na2S, and measuring spectra after 120 minutes at 30°C with specific slit widths and voltages.

5：Data Analysis Methods:

Detection limits were calculated using standard deviation and slope of concentration curves. Fluorescence quantum yields were determined using quinine sulfate as a reference. Molecular orbital distributions were analyzed with Multiwfn Program.