Influence of bismuth doping on the structural, optical characteristics and radiation attenuation properties of zinc sulfide quantum dots

The co-precipitation technique was utilized to synthesize ZnS quantum dots (QDs) doped with varying concentrations of Bi (0%, 2.5%, 6.5%, and 10.5%). Structural and optical properties were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV–visible spectroscopy. XRD analysis revealed cubic structures with preferential plane orientation (111) and crystallite sizes ranging from 4.5 nm to 2.5 nm for the QDs. TEM images exhibited agglomerated shapes. FTIR spectroscopy indicated that the intensity of FTIR decreased after Bi-doping. The optical properties of Bi-doped ZnS QDs significantly impacted the optical band gap (E_g), showing a blue shift compared to bulk cubic ZnS due to quantum confinement effects, with E_g values ranging from 3.761 to 3.899 eV, increasing with higher Bi concentrations. The nuclear shielding effectiveness of pristine and Bi-doped ZnS QDs was evaluated, with results indicating superior protection against nuclear radiations for Bi-doped ZnS QDs with the smallest nanoparticle size.