Synthesis and photoluminescent and nonlinear optical properties of manganese doped ZnS nanoparticles

In this work we synthesized ZnS:Mn2+ nanoparticles by chemical method using PVP (polyvinylpyrrolidone) as a capping agent in aqueous solution. The structure and optical properties of the resultant product were characterized using UV–vis optical spectroscopy, X-ray diffraction (XRD), photoluminescence (PL) and z-scan techniques. UV–vis spectra for all samples showed an excitonic peak at around 292 nm, indicating that concentration of Mn2+ ions does not alter the band gap of nanoparticles. XRD patterns showed that the ZnS:Mn2+ nanoparticles have zinc blende structure with the average crystalline sizes of about 2 nm. The room temperature photoluminescence (PL) spectrum of ZnS:Mn2+ exhibited an orange-red emission at 594 nm due to the 4T1–6A1 transition in Mn2+. The PL intensity increased with increase in the Mn2+ ion concentration. The second-order nonlinear optical properties of nanoparticles were studied using a continuous-wave (CW) He–Ne laser by z-scan technique. The nonlinear refractive indices of nanoparticles were in the order of 10−8 cm2/W with negative sign and the nonlinear absorption indices of these nanoparticles were obtained to be about 10−3 cm/W with positive sign.