Effect of M = Fe3+, Cr3+, Sn2+, and Mg2+ Substitution on the Structural and Optical Properties of Zn0.99 M0.01 S NPs

The Zn0.99 M0.01 S (M = Fe3+, Cr3+, Sn2+, and Mg2+) NPs were synthesized by applying the co-precipitation technique. The produced NPs’ structural, optical, and functional groups were identified by a variety of methods, including X-ray diffraction (XRD), UV-Vis Spectroscopy, Photoluminescence (PL), and Fourier transform infrared spectroscopy (FTIR). A cubical structure and strong XRD intensity were detected in the (111) plane direction of the generated nanoparticles. The Lattice parameter decreased with the doping concentrations mentioned above (~5.4–5.3 Å), and the average crystallite size of the nanoparticles fell between 1.8 and 4.3 nm. According to UV-Vis spectroscopy, the absorption edge moved to longer wavelengths with Cr3+, Sn2+, and Mg2+ concentrations. Moreover, Fe3+ doped ZnS NPs indicate that the absorption edge shifts toward a shorter wavelength side. The UV-vis spectra narrowed to 4.08, 4.10, 3.99, 3.85, and 3.89 eV, respectively, are used to estimate the energy band gap (Eg) of pure ZnS, Fe3+, Cr3+, Sn2+, and Mg2+ doped ZnS NPs. Photoluminescence investigations revealed that pure ZnS NPs emitted deep-level emission (DLE) at 685 nm and near band-edge (NBE) at 435 nm. PL intensity rises with the addition of Mg2+ and Cr3+ to ZnS. Conversely, ZnS will be quenched by the concentration of Fe3+ and Sn2+ through a non-radioactive decay mechanism. The FTIR spectrum revealed the presence of functional groups in the prepared NPs.