Enhanced optical properties of ZnSexS1-x and Mn-doped ZnSexS1-x QDs via non-toxic synthetic approach

Abstract

A tunable approach for the non-phosphine synthesis of monodisperse, highly photoluminescent ZnSexS1-x and Mn-doped ZnSe0.1S0.9 quantum dots (QDs) using (Z)-1-(octadec-9-enyl)-3-phenylselenourea and (Z)-1-(octadec9-enyl)-3-phenylthiourea as novel sources of selenium and sulphur is provided. QDs syntheses were performed in an organic disperse medium at 280 degrees C using environmentally friendly and at the same time highly reactive N,N'disubstituted thio- and selenoureas. By varying the molar ratios of sulphur and selenium sources, ZnSexS1-x QDs, where x = 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, and 0.75, were obtained. Mn-doped ZnSe0.1S0.9 QDs (0.5-15 molar %) have been synthesized by the low cost hot-injection method. The presence of manganese in ZnSe0.1S0.9 QDs resulted in the appearance of the expected second emission band (579 nm), the maximum intensity of which was determined for Mn(5%):ZnSe0.1S0.9 QDs. According to the analytical data, ZnSexS1-x and Mn-doped ZnSe0.1S0.9 QDs are consistent with the desired elemental composition and uniform in size. The chemical composition, morphology and crystal structure of prepared undoped ZnSexS1-x and Mn-doped ZnSe0.1S0.9 QDs were studied by X-Ray diffraction (XRD), energy dispersive X-Ray spectroscopy (EDS), X-Ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) analyses. The optical properties of nanocomposite materials based on synthesized ZnSexS1-x and Mn-doped ZnSe0.1S0.9 QDs in a polymer matrix of polyvinyl toluene (PVT) were also studied. It should be noted that transparent monoliths have the same photoluminescent characteristics as QDs. These results give proof of the chemical stability of the resulting nanomaterials and can contribute to their possible transfer in the photodetectors and LEDs production.