1：Experimental Design and Method Selection:

The study employs a FRET-based strategy due to the spectral overlap between GCPF fluorescence and PA absorption. The synthesis of GCPF is optimized for high quantum yield and stability.

2：Sample Selection and Data Sources:

Chitosan and glutaraldehyde are used as raw materials. PA and other nitroaromatic compounds are used for selectivity tests. Real lake water samples are used for application validation.

3：List of Experimental Equipment and Materials:

Materials include chitosan, glutaraldehyde, picric acid, and various chemicals from suppliers like Aladdin Reagent Co. Ltd. Equipment includes a Perkin Elmer LS55 luminescence spectrometer, SU8020 scanning electron microscope, FLS1000 fluorescence spectrometer, ZF-20D ultraviolet analyzing equipment, and S-25 digital pH meter.

4：Experimental Procedures and Operational Workflow:

GCPF is synthesized by stirring chitosan and GA with acetic acid. PA detection involves mixing GCPF with PA in phosphate buffer, vortexing, and measuring fluorescence after 2 minutes. Real sample analysis includes ultrafiltration of lake water and standard addition methods.

5：Data Analysis Methods:

Fluorescence spectra are recorded, and data are analyzed using linear regression for calibration curves. Quantum yield is calculated by comparison with quinine sulfate. FRET parameters like overlap integral and F?rster distance are computed based on literature methods.