Photoluminescence spectra of ZnS:X− (X = F and I) nanoparticles synthesized via a solid-state reaction

ZnS:X− (X = F and I) nanoparticles have been prepared successfully via a solid-state method at low temperature, and the effects of doping with X− on the photoluminescence (PL) properties of ZnS nanoparticles have been investigated. X-ray powder diffraction (XRD), energy-dispersive X-ray spectrum (EDS), transmission electron microscope (TEM), ultraviolet-visible diffusion reflection spectra, and emission and excitation spectra were used to characterize the crystal structure, chemical compositions, diameter, surface states, and optical properties of ZnS:X− (X = F and I) nanoparticles. XRD studies showed the phase singularity of ZnS:X− particles having zinc-blende (cubic) structure with an average crystallite size 4.7-11.0 nm. The results indicated that the PL of doping halogen ZnS nanoparticles can be enhanced remarkably by controlling suitable halogen doping, and the most intense emission was obtained when X/Zn = 0.3 and 0.45 under 387 nm excitation corresponding to X = F and I, respectively. The emission intensity of ZnS:F− (F/Zn = 0.3) nanoparticles was higher than that of ZnS:I− (I/Zn = 0.45), and exhibited strong emission with an intensity about 9 times higher than the undoped nanoparticles. It was found that the PL of ZnS nanoparticles doped with various halogens was decreased with the increase of the halogen ion radius.