1：Experimental Design and Method Selection:

The study employed a one-step electrolysis method to synthesize P, S-GQDs using a graphite electrode, sodium phytate, and sodium sulfide in an alkaline solution. The ECL properties of the synthesized GQDs were evaluated.

2：Sample Selection and Data Sources:

High-purity graphite rods were used as the anode in the electrolysis process. The synthesized P, S-GQDs were characterized and used to develop an ECL immunosensor for OA detection.

3：List of Experimental Equipment and Materials:

Equipment included a transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), UV-Vis spectrophotometer, fluorescence spectrometer, and electrochemical workstation. Materials included sodium phytate, sodium sulfide, NaOH, graphite rods, and various chemicals for electrode modification and antibody conjugation.

4：Experimental Procedures and Operational Workflow:

The synthesis of P, S-GQDs involved electrolysis of a graphite rod in a solution containing sodium phytate, Na2S, and NaOH. The resulting GQDs were characterized and conjugated with anti-OA-MAb to form an ECL immunoprobe. A competitive indirect ECL immunosensor was developed using CMCNT-PDDA-AuNCs as the sensing platform.

5：Data Analysis Methods:

The ECL intensity was measured and plotted against OA concentrations to determine the IC50 and LOD values. The immunosensor's performance was evaluated through recovery tests in mussel samples.