1：Experimental Design and Method Selection:

A one-pot synthesis method was used to prepare CuS and rGO capped CuS nanocomposites via a redox transformation reaction between Cu and graphene oxide without additives. Various characterization techniques (UV–vis DRS, PL, XRD, SEM, TEM, BET, FTIR, impedance analyzer) were employed to study optical, structural, morphological, and electrical properties.

2：Sample Selection and Data Sources:

Samples included CuS nanoparticles and rGO capped CuS composites synthesized from Cu(CH3COO)2.5H2O, Na2S.9H2O, and rGO derived from graphite powder using a modified Hummers method.

3：5H2O, Na2S.9H2O, and rGO derived from graphite powder using a modified Hummers method. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included Philips X’pert x-ray diffractometer, Zeiss EVO 18 SEM, Technai G2 TEM, RF-5301PC spectrofluorometer, UV-3600 spectrophotometer, Shimadzu FTIR spectrophotometer, ASAP 2020 Micromeritics BET analyzer, Shimadzu DTG-60H TGA, HIOKI 3532 LCR HITESTER, Keithley 2400 system digital electrometer. Materials included Cu(CH3COO)2.5H2O, Na2S.9H2O, graphite powder, H2SO4, KMnO4, H2O2, NaNO3, ethanol, double distilled water.

4：5H2O, Na2S.9H2O, graphite powder, H2SO4, KMnO4, H2O2, NaNO3, ethanol, double distilled water. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Synthesis involved preparing rGO from graphite, then mixing Cu(CH3COO)2.5H2O with rGO solution, adding Na2S solution, stirring, centrifuging, washing, and drying. Characterization steps included XRD for structure, SEM/TEM for morphology, UV–vis/PL for optical properties, FTIR for functional groups, BET for surface area, TGA for thermal stability, and impedance/conductivity measurements using LCR tester and four-probe method.

5：5H2O with rGO solution, adding Na2S solution, stirring, centrifuging, washing, and drying. Characterization steps included XRD for structure, SEM/TEM for morphology, UV–vis/PL for optical properties, FTIR for functional groups, BET for surface area, TGA for thermal stability, and impedance/conductivity measurements using LCR tester and four-probe method. Data Analysis Methods:

5. Data Analysis Methods: Data analysis involved calculating dielectric constant from capacitance, impedance from conductance/capacitance, electrical conductivity from resistance, activation energy from Arrhenius plots, and using Scherrer equation for particle size.