1：Experimental Design and Method Selection:

A one-step hydrothermal synthesis method was used to synthesize water-soluble purple-emissive carbon dots (p-CDs) from folic acid. The reaction conditions were optimized in terms of pH, temperature, and time.

2：Sample Selection and Data Sources:

Folic acid was used as the sole precursor. The optical properties of p-CDs were studied in diluted aqueous solution at room temperature.

3：List of Experimental Equipment and Materials:

TEM (JEM-2010F microscope), AFM (NTegra Spectra microscope), XPS (PHI VersaProbe II spectrometer), FTIR (Nicolet iS FTIR spectrometer), Raman (DXR Raman microscope), UV–vis spectrophotometer (Specord S 600), fluorescence spectrometer (FLS980), and photoresponsivity measurement setup.

4：Experimental Procedures and Operational Workflow:

The synthesis involved dissolving folic acid in water, adjusting the pH, hydrothermal treatment, purification, and characterization. The p-CDs were then integrated into a Si photodetector to measure photoresponsivity enhancement.

5：Data Analysis Methods:

The PL decays were fitted using a multi-exponential function. The PL QY was determined by an absolute method using an integrating sphere.