1：Experimental Design and Method Selection:

The N,S-CQDs were synthesized using a one-pot hydrothermal method with thiamine nitrate (TN) as the single material. The properties of N,S-CQDs were characterized by TEM, XPS, FTIR, fluorescence (FL), and UV-vis spectrophotometer.

2：Sample Selection and Data Sources:

The study focused on detecting VB12 and tartrazine in milk and beverages. Samples were pretreated by heating and acidification, followed by centrifugation and filtration.

3：List of Experimental Equipment and Materials:

Equipment included a JEM-2100 TEM, Nicolet-6700 FT-IR spectrometer, ESCALAB250Xi XPS, FLS980 fluorescence spectrophotometer, Cary eclipse fluorescence spectrofluorimeter, and UV-2550 spectrophotometer. Materials included TN, VB12, tartrazine, and various chemicals for buffer preparation.

4：Experimental Procedures and Operational Workflow:

The synthesis of N,S-CQDs involved hydrothermal treatment of TN, followed by purification. The detection of VB12/tartrazine involved mixing N,S-CQDs with the sample in B-R buffer, incubating, and recording FL spectra.

5：Data Analysis Methods:

The FRET theory was applied to analyze the interaction between N,S-CQDs and VB12/tartrazine. The quantum yield, energy transfer efficiency (E%), and rate (KT) were calculated using specific equations.