Optical Properties of Ni²⁺-, Co²⁺-, and Mn²⁺-doped ZnS Nanoparticles Synthesized Using Reverse Micelle Method

Zn1−xYxS (x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) was prepared by reverse micelle method using sodium bis(2-ethylhexyl)sulfosuccinate (AOT) as surfactant; Y refers to Ni2+, Co2+, and Mn2+ ions. The effects of ion doping on the optical characterization, structure, and morphology of ZnS were investigated using ultraviolet-visible (UV-vis) spectroscopy, photoluminescence (PL) spectrophotometry, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy, and transmission electron microscopy. FT-IR and EDAX results confirmed the incorporation of ion dopants into ZnS crystal structure, and XRD results showed that ZnS:Y nanoparticles crystallized in a zinc blende structure without any impurity. The particle size of all of samples ranged from 2 nm to 4 nm, as calculated by the Debye–Scherrer formula and Brus equation. Ion doping shifted the absorption edge to lower wavelengths, as shown in the obtained UV-vis spectra of samples. Bandgap energy values ranged from 4.1 eV to 4.9 eV. PL characteristics of the doped ZnS were compared, and ZnS:Mn2+ was found to have the highest PL intensity ratio (33.86%). The increased PL intensity ratio indicated increased homogeneous nanoparticle growth with decreased surface defects.