1：Experimental Design and Method Selection:

The study involves synthesizing Au and AuAg nanoclusters using β-lactoglobulin as a capping and reducing agent, with adjustments in AgNO3 concentration and addition order to achieve color-tunable fluorescence. Methods include UV-vis spectroscopy, fluorescence spectroscopy, XPS, TEM, and zeta potential measurements to characterize the nanoclusters.

2：Sample Selection and Data Sources:

Samples include β-lactoglobulin, HAuCl4, AgNO3, and various amino acids. Data are acquired from synthesized nanoclusters and their interactions with L-cysteine.

3：List of Experimental Equipment and Materials:

Equipment includes UV-vis Cary 60 spectrophotometer, Hitachi F-7000 fluorescence spectrophotometer, VG Thermo ESCALAB 250 XPS spectrometer, Tecnai G2 F30 S-TWIN TEM, and Zetasizer Nano-ZEN3700 for zeta potential. Materials include β-lactoglobulin, HAuCl4, AgNO3, NaOH, amino acids, and ultrapure water.

4：Experimental Procedures and Operational Workflow:

Synthesis involves mixing HAuCl4 and AgNO3 with β-Lg at pH 12, incubating at 37°C for 12 hours, and purifying by centrifugation. Detection of Cys involves mixing nanoclusters with Cys solutions and recording fluorescence spectra.

5：Data Analysis Methods:

Fluorescence intensity changes are analyzed to calculate enhanced or quenched efficiencies, with linear relationships established for Cys concentration ranges. Statistical analysis includes recovery and RSD calculations for cell samples.