1：Experimental Design and Method Selection:

Hydrothermal treatment was strategically employed to synthesize water-soluble HFCNs using 5-amino salicylic acid as the carbon source.

2：Sample Selection and Data Sources:

5-amino salicylic acid was dissolved in ultrapure water and subjected to hydrothermal treatment at 220°C for 4 h.

3：List of Experimental Equipment and Materials:

JEOL JEM-2100 transmission electron microscope, AFM Bruker multimode

4：0, Zetasizer Nano ZS90, multispectral fluorescence in vivo molecular imaging system, Bruker Senterra dispersive Raman microscopy, AXISULTRA DLD X-ray photoelectron spectrometer, Thermo Scientific Nicolet iS50 FT-IR Spectrometer, HITACHI U-2910 UV-Vis Spectrophotometer, Hitachi F-4500 spectrophotometer, FLS 920 time-correlated single-photon counting system, Zeiss LSM880 confocal laser-scanning microscope. Experimental Procedures and Operational Workflow:

The cloudy solution was poured into a 50 mL Teflon-lined stainless steel autoclave and maintained at 220°C for 4 h. After cooling, the mixture was centrifuged and dialyzed.

5：Data Analysis Methods:

The fluorescence emission spectra were recorded, and the relationship between PL intensity and pH values was analyzed.