Zinc sulfide quantum dots as powerful and efficient nanophotocatalysts for the removal of industrial pollutant

Abstract

In this work, a simple, efficient and powerful photocatalytic methodology based on application of pure zinc sulfide (ZnS) quantum dots (QDs) is presented for the removal of naphthalene, as a model molecule of industrial pollutants. A facile room-temperature precipitation method was applied for the synthesis of ZnS QDs, in the presence of 2-mercaptoethanol as capping agents. The characterization of the prepared QDs was carried out by X-ray diffraction (XRD), transmission electron microscopy, high-resolution scanning electron microscopy, scanning tunneling microscopy, fluorescence, and UV–Vis absorption spectroscopies. The XRD investigations indicated that the prepared ZnS QDs are crystalline, with cubic zinc blend structure, with the average particle diameters of 1.2 nm. The fluorescence and UV–Vis absorption investigations showed a narrow and sharp emission band at 424 nm with a broad adsorption band around 235 nm. In addition, the prepared ZnS QDs were used as nanophotocatalysts, for the removal of naphthalene, as a model molecule. The influence of the experimental parameters on the removal efficiency of the ZnS QDs was studied. According to the results, the highest photocatalytic degradation of naphthalene in the presence of ZnS QDs (>95 %) was obtained at alkaline pH, in the presence of 10 mg of QDs, after a reasonable reaction time.