1：Experimental Design and Method Selection

The study involved the preparation of carbon quantum dots (CQDs) via one-step hydrothermal treatment, followed by their exfoliation into single-layered graphene quantum dots (s-GQDs) using methanol. The interaction between s-GQDs and Dy3+ ions was explored to induce aggregation and emission quenching, which was then reversed by phosphate ions for detection purposes.

2：Sample Selection and Data Sources

Artificial wetlands water samples were collected and filtered for phosphate detection. Standard solutions of phosphate and Dy3+ were prepared for calibration and testing.

3：List of Experimental Equipment and Materials

Dysprosium sulfate, sodium phosphate, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), triethylamine (TEA), methanol, and other chemicals were used. Equipment included a fluorescence spectrophotometer, TEM, HRTEM, AFM, XPS, FTIR spectrometer, and others.

4：Experimental Procedures and Operational Workflow

The procedure involved the synthesis of CQDs, their exfoliation into s-GQDs, characterization of s-GQDs, investigation of Dy3+-induced aggregation and quenching, and the selective detection of phosphate through fluorescence recovery.

5：Data Analysis Methods

Fluorescence spectra were analyzed to determine the quenching and recovery effects. TEM, AFM, XPS, and FTIR were used for material characterization.