1：Experimental Design and Method Selection:

The method is based on the quenching of silicon nanoparticles (SiNPs) fluorescence by CoOOH nanoparticles via surface energy transfer (SET) and inner filter effect (IFE), and its recovery upon decomposition of CoOOH by vitamin C through a redox reaction.

2：Sample Selection and Data Sources:

SiNPs and CoOOH NPs were synthesized according to literature methods. Vitamin C samples included standard solutions and real samples (red grape, orange juice, vitamin C tablets).

3：List of Experimental Equipment and Materials:

Equipment includes UV2450 spectrophotometer, F-7000 spectrophotometer, JEOL-2100 transmission electron microscope, FLS 920 time-resolved fluorescence spectrometer. Materials include (3-Aminopropyl) trimethoxysilane (APTMS), HEPES buffer, and other analytical grade reagents.

4：Experimental Procedures and Operational Workflow:

SiNPs and CoOOH NPs were mixed in HEPES buffer, incubated with vitamin C for 20 minutes at 20°C, and fluorescence spectra were recorded at 350 nm excitation. Real samples were pre-treated by filtration and dilution.

5：Data Analysis Methods:

Fluorescence intensity was measured, and data were analyzed using the Stern-Volmer equation. Detection limit was calculated based on standard deviation and slope of the calibration curve.