Tuning Structural and Optical Properties of Cu-Doped CdS Nanoparticles via Controlled Bandgap Engineering

Cadmium sulfide (CdS) nanoparticles doped with copper (Cd1 – xCuxS) are synthesized using a chemical co-precipitation method to investigate the effect of Cu incorporation on the structural and optical properties, with particular emphasis on bandgap modulation. X-ray diffraction (XRD) analysis confirms the formation of a single-phase hexagonal CdS crystal structure without any detectable secondary phases, indicating the successful incorporation of Cu into the host lattice. A gradual reduction in crystallite size from 3.73 nm to 2.89 nm is observed with increasing Cu concentration. A slight decrease in the lattice parameters and unit cell volume further supports the substitution of Cd2+ ions by the relatively smaller Cu2+ ions.Field Emission Scanning Electron Microscopy (FESEM) reveals nanostructured particles with moderate agglomeration, while Cu incorporation improves particle size uniformity. Energy Dispersive X-ray Analysis (EDAX) confirms the presence of Cd, S, and Cu elements and shows no evidence of impurity phases, verifying the successful incorporation of Cu into the CdS lattice. The optical properties are examined using UV-Visible spectroscopy, which shows a progressive blue shift in the absorption edge with increasing Cu content. The optical bandgap increases from 2.08 eV for pristine CdS to 2.15 eV and 2.16 eV for the Cu-doped compositions. This bandgap widening is attributed to the combined influence of quantum confinement arising from the reduced crystallite size and lattice distortion associated with Cu substitution. These findings demonstrate that Cu doping provides an effective approach for tuning the structural and optical properties of CdS nanoparticles, highlighting their potential for optoelectronic and photocatalytic applications.