1：Experimental Design and Method Selection:

The study involved the development of an electrochemical aptasensor using GQD-Au hybrid nanoparticles for the detection of vitamin D3. The methodology included the synthesis and characterization of GQD-Au hybrid nanoparticles, fabrication of the aptasensor, and its electrochemical characterization.

2：The methodology included the synthesis and characterization of GQD-Au hybrid nanoparticles, fabrication of the aptasensor, and its electrochemical characterization. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Vitamin D3 aptamer was used as the bio-recognition element. Serum samples spiked with known concentrations of vitamin D3 were used for testing the sensor's performance.

3：List of Experimental Equipment and Materials:

Micrux Standard Electrodes (Au-μE), chloroauric acid, EDC-HCl, NHS, MU, MUA, and other chemicals were used. Equipment included HR-TEM, FTIR, UV-Vis spectroscopy, XRD, and an impedance analyzer.

4：Experimental Procedures and Operational Workflow:

The aptasensor was fabricated by immobilizing MU:MUA on Au-μEs, followed by activation with EDC-NHS, immobilization of GQD-Au hybrid nanoparticles, and coating with aptamer. EIS was performed to characterize the sensor.

5：Data Analysis Methods:

The performance of the aptasensor was evaluated based on linear range, LOD, LOQ, sensitivity, specificity, stability, and recovery in serum samples.