Evaluation of structural, optical, and scintillation characteristics of Ag activated ZnS nanoparticles

Abstract

The ZnS nanoparticles activated with various concentrations of Ag and co-activated with Cl ions were synthesized hydrothermally and sintered under controlled environment at 960 °C. The transition from cubic to hexagonal phase and presence of some fraction of ZnO were detected with powders X-rays diffraction (PXRD) and confirmed by energy dispersive X-rays (EDX) analysis as well. An increase in particle sized from ∼450 nm to ∼700 nm was observed with increase in Ag doping concentration in the synthesized ZnS nanoparticles. The optical band gap was found lower for the synthesized ZnS nanoparticles as compared to the reported optical band gap for ZnS, which can be assigned to defect states. Emission bands peaking at ∼2.68 eV and 2.35 eV were observed due to the characteristics ZnS, and ZnO luminescence, respectively. A significant improvement in the emission intensity by about 2.3 orders of magnitude with increase in Ag doping concentration were observed as compared to pristine ZnS nanoparticles. For the samples having higher concentrations of O atoms the quenching in luminescence intensity were found which can be assigned to the trapping of charge carriers by O defects states. The scintillation light yield enhanced with increase in Ag doping concentration and showed similar quenching behavior as observed for photoluminescence. A faster decay time response with suppression of afterglow were observed for ZnS nanoparticles as compared to commercial micron size ZnS phosphors.