<p>Sensitive and selective detection of cadmium ions is important to pollution monitoring and human health. In this work, zinc sulfide (ZnS) nanoparticles (NPs) doped by Gd cations and coated with cetyltrimethylammonium bromide (CTAB) surfactant molecules were prepared by wet chemical method in water. The synthesized multifunctional material exhibited a high degree of crystallinity and good uniformity in both size and shape. On the other hand, the optical measurement revealed high UV response by the ZnS/Gd@CTAB nanocomposite. Deep characterization techniques were performed to further go insight into the microstructure of the prepared multifunctional ZnS/Gd@CTAB system. The electrochemical performance of ZnS/Gd@CTAB-modified glassy carbon electrodes for Cd²⁺ ion detection was thoroughly investigated. The sensors exhibited remarkable sensitivity, featuring a detection limit (LOD) of 0.05&#xa0;µM (S/N = 3) and a wide linear range of 0.05–10&#xa0;µM. When tested in real water samples, the modified electrodes demonstrated remarkable resilience and analytical reliability, maintaining stability and repeatability with recovery rates ranging from 95.6 to 104.5%. The electrode platform improves the accumulation and electron-transfer kinetics for Cd²⁺ by combining the advantageous charge-transfer characteristics of ZnS-based nanomaterials with the surface-active and dispersion-enhancing effects of Gd-doping and CTAB functionalization. These findings together validate the promise of ZnS/Gd@CTAB-functionalized electrodes as a viable, efficient, and selective platform for sensitive cadmium monitoring in environmental water analysis.</p>