Synthesis of ZnS nanoparticles and the investigation of their structural, optical and electrical properties

The investigated ZnS nanoparticles (NPs) stabilized by L-Cysteine (C₃H₇NO₂S) were synthesized at 100 °C in basic aqueous solution using the nucleation-doping strategy. To study the optical, structural, and microstructural properties of the elaborated NPs (ZnS), UV–Vis spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were adopted. Both Scherrer equation and Williamson–Hall relations were employed to determine the ZnS particle size. The obtained results show that the prepared ZnS particles are quasi-spherical NPs with a size distribution of about 3–4 nm. This result is established by the HRTEM analysis. From the optical study, the estimated ZnS band gap is about 4.07 eV. Impedance analysis confirms the important contribution of the insulator boundaries to the charges dynamic in the studied structure. In addition, it is observed that the electrical characteristics and the relaxation phenomena are associated to the same origin. The term “conductivity spectra” was suggested by Elliott who successfully described using the correlated barrier-hopping model. These spectra of the material, at numerous temperatures, are described using the Bruce (double Jonscher power) law. The electrical DC conductivity study indicates the semiconductor (SC) character of the NPs. At high temperatures, the SC behavior was related to the activation of the small polaron hopping conduction process. The Nyquist configuration confirms the contribution of both conductive grain and resistive boundaries regions to the transport phenomena of the ZnS. From such study, we conclude that the hopping and relaxation processes are thermally activated. These findings suggest that the elaborated NPs, with their unique electrical and optical properties, could be further explored for potential applications in environmental remediation technologies, such as photocatalytic degradation of pollutants, or in sustainable energy solutions, contributing to environmentally friendly innovations.