Morphology engineering and growth mechanism of ZnS nanostructures synthesized by solvothermal process

Abstract

Zinc sulfide (ZnS) nanostructures with various morphologies play an imperative role in optoelectronic applications. In this study, different ZnS nanostructures with well-defined morphologies were synthesized in a controlled manner by a low-temperature solvothermal method using the binary solvent mixtures of ethylenediamine and water (EN/W). Controlling the content of EN and the growth temperature, ZnS nanostructures including nanoflowers, nanoflakes, nanorods, and hexagonal nanoplates were produced at a very low temperature ranging from 100 °C to 180 °C during short reaction times of 2 h and 6 h with excellent reproducibility. X-ray diffraction patterns of the nanostructures considerably revealed the single crystalline nature with a pure wurtzite phase of ZnS even at the low growth temperature having the average crystallite size in the range of 12.8–25.0 nm. The morphology evolution of the samples showed that there is a strong correlation between the morphologies of the ZnS nanostructures and the variations of both the growth temperature and reaction solvent. Based on the experimental results, a growth mechanism was also proposed for all the ZnS nanostructures with different morphologies. A sharp absorption band-edge was found for the ZnS nanostructures, in which the optical bandgap energy was laid ranging from 3.97 eV to 4.09 eV due to the quantum confinement effect. All the samples featured a broad asymmetrical photoluminescence emission with multiple peaks, corresponding to excitonic and trapped luminescence centers. The effect of morphology on the optoelectronic performance resulted in a tremendous photoresponsivity and an excellent time-response switching behavior in UV region.