1：Experimental Design and Method Selection:

Hydrothermal synthesis of CQDs from ginkgo leaves, characterization by transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy.

2：Sample Selection and Data Sources:

Ginkgo leaves as carbon source, A549 and HeLa cells for cytotoxicity and bioimaging studies, lake water and serum samples for Hg2+ detection.

3：List of Experimental Equipment and Materials:

High-resolution transmission electron microscope, spectrofluorometer, X-ray diffractometer, X-ray photoelectron spectrometer, FT-IR spectrometer, UV-Vis spectrophotometer, hydride-generation atomic fluorescence spectrophotometer, high-speed centrifuge, fluorescence-inverted microscope, ultrasonic cleaning machine, electronic balance, ELISA instrument.

4：Experimental Procedures and Operational Workflow:

Synthesis of CQDs, cytotoxicity testing using MTT assay, bioimaging of HeLa cells, detection of Hg2+ in samples.

5：Data Analysis Methods:

Fluorescence spectroscopy for Hg2+ detection, statistical analysis of cytotoxicity and bioimaging results.