1：Experimental Design and Method Selection:

The study involved the synthesis of CdS nanorods modified with Au and graphene quantum dots (GQDs) through solvothermal and reflux methods. The PEC sensor was designed to detect Cu2+ ions in water samples.

2：Sample Selection and Data Sources:

Real water samples were used to test the sensor's performance. The samples were prepared with varying concentrations of Cu2+ ions to establish a calibration curve.

3：List of Experimental Equipment and Materials:

Equipment included a field emission scanning electron microscope (FEI Quanta SEM Model 400 F), transmission electron microscopy (Hitachi, HT-7700), X-ray photoelectron spectroscopy (Kratos Axis Ultra XPS spectrometer), and a photoluminescence analysis system (Renishaw inVia Raman microscope). Materials included cadmium acetate dihydrate, thiourea, chloroauric acid, trisodium citrate, and graphene quantum dots.

4：Experimental Procedures and Operational Workflow:

The CdS NRs were synthesized via a solvothermal process, followed by the preparation of Au NPs/GQDs and their integration with CdS NRs. The PEC sensor electrodes were prepared using a doctor blade method, and PEC experiments were conducted under light illumination.

5：Data Analysis Methods:

The photocurrent responses were analyzed to determine the sensor's sensitivity and selectivity towards Cu2+ ions. The data was processed using ImageJ software for particle size analysis.