Photoluminescence of wurtzite-type Ce-doped ZnS nanocrystals processed by a low-temperature aqueous solution approach

Abstract

Undoped and Ce-doped ZnS nanocrystals with hexagonal wurtzite structure were synthesized by a low-temperature aqueous solution method that uses l-cysteine as complexing and capping agent. The morphology analysis revealed the formation of polydisperse nanocrystals with sizes in the range of 2–4 nm, while the energy dispersive X-ray spectroscopy showed that all the samples were sulfur deficient. The presence of Ce3+ species in the Ce-doped samples was confirmed by the X-ray photoelectron spectroscopy technique. UV–vis spectroscopy indicated that all samples had a blue shift of optical bandgap compared to bulk ZnS. According to the room-temperature photoluminescence studies, the spectra of Ce-doped ZnS nanocrystals exhibited a broad band emission consisting of UV and blue components, associated with ZnS defects, and a green component due to the 5d-4f transition of Ce3+.