1：Experimental Design and Method Selection:

The study employs a hydrothermal method for one-pot green synthesis of carbon dots using waste tea extract as a carbon source, with characterization via UV-visible, fluorescence, FT-IR, TEM, XPS, and XRD. The design includes evaluating antioxidant properties and developing fluorescent sensors for metal ions and biomolecules.

2：Sample Selection and Data Sources:

Waste tea was purchased from a tea line in Henan, Kaifeng. Metal salts and chemicals were bought from Aladdin Industrial Inc. Real samples include tap water, VC effervescent tablets, and human urine.

3：List of Experimental Equipment and Materials:

Equipment includes a TU-1900 spectrophotometer, Edinburgh FS5 spectrofluorometer, JEM-2100 TEM, Bruker D8 Advance diffractometer, Thermo Nicolet Avatar 360 spectrometer, and Thermo ESCALAB 250XI photoelectron spectrometer. Materials include waste tea, ascorbic acid, L-cysteine, ethanediamine, and various metal salts.

4：Experimental Procedures and Operational Workflow:

Tea-CDs are prepared by hydrothermal treatment of waste tea extract with ethanediamine at 150°C for 6 hours, followed by centrifugation and freeze-drying. Antioxidant assays involve Fenton reaction and pyrogallol autoxidation. Detection procedures involve mixing Tea-CDs with analytes, incubating for 1 minute, and measuring fluorescence intensity at 350 nm excitation.

5：Data Analysis Methods:

Fluorescence intensity data are analyzed for linear relationships and detection limits. Scavenging rates are calculated using specific equations. Statistical analysis includes recovery rates and RSD from triplicate experiments.