1：Experimental Design and Method Selection:

The study employs a turn-on fluorometric method based on aggregation-induced emission enhancement (AIEE) of GSH-capped Au NCs triggered by Ce3+ ions. Cysteine detection is achieved through its interaction with Ce3+ and Au NCs, leading to enhanced fluorescence.

2：Sample Selection and Data Sources:

Cysteine samples, various amino acids, and HepG2 cells were used. Reagents included cerium nitrate, glutathione, hydrogen tetrachloroaurate(III) tetrahydrate, amino acids, DAPI, and cell culture materials.

3：List of Experimental Equipment and Materials:

Equipment includes F-2700 spectrofluorophotometer, UV-1700 UV-Vis spectrometer, Hitachi H-800 TEM, Bruker IFS66V FT-IR spectrometer, RF-5301PC spectrofluorophotometer, Leica SP5II CLSM, PHS-3C pH meter, and water bath. Materials include Au NCs, Ce3+, Cys, Tris-HCl buffer, and cell imaging reagents.

4：Experimental Procedures and Operational Workflow:

For Cys detection, Au NC, Ce3+, and Cys were mixed in Tris-HCl buffer, incubated for 30 min, and fluorescence measured at 360/575 nm. For cell imaging, HepG2 cells were treated with NEM, Au NC, Ce3+, and Cys, followed by fixation, permeabilization, staining with DAPI and antibodies, and imaging with CLSM.

5：Data Analysis Methods:

Fluorescence intensity changes were analyzed to quantify Cys concentration, with linear regression applied to the fluorescence intensity ratio versus logarithm of Cys concentration. Specificity was assessed by testing interference from other amino acids and compounds.