1：Experimental Design and Method Selection:

The study involved synthesizing g-C3N4 nanofibers by hydrolyzing bulk g-C3N4 in NaOH solution, characterizing them using TEM, XRD, FT-IR, and XPS, and using them as a fluorescent probe for dopamine detection via fluorescence quenching and FRET mechanisms.

2：Sample Selection and Data Sources:

Dopamine and other interfering substances (e.g., uric acid, ascorbic acid) were obtained from Sinopharm Chemical Reagent Co., Ltd., and human serum samples were purchased from Beijing GMP workstation.

3：List of Experimental Equipment and Materials:

Equipment included Transmission electron microscopy (JEOLJEM-2100), X-ray diffractometer (Bruker), FT-IR spectrometer (Nicolet islo), XPS spectrometer (Thermo ESCALAB 250), fluorescence spectrophotometer (FL3-TCSPC), and UV-vis spectrophotometer (UV-220). Materials included melamine, NaOH, and various chemicals for interference studies.

4：0). Materials included melamine, NaOH, and various chemicals for interference studies. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Bulk g-C3N4 was synthesized from melamine pyrolysis, then hydrolyzed in NaOH to form nanofibers, which were dialyzed and freeze-dried. Fluorescence detection was performed by adding dopamine to the probe solution and measuring intensity changes at 350 nm excitation.

5：Data Analysis Methods:

Data were analyzed using linear regression for calibration curves, Stern-Volmer equation for quenching kinetics, and statistical methods for recovery and RSD calculations in real samples.