Synthesis of ZnSe QDs: Effects of stabilizer on the optical properties and structural morphology

Abstract

• ZnSe QDs were synthesized in an aqueous phase using stabilizing ligands −MPA, GSH, and a combination of MPA-GSH. • The choice of stabilizer significantly affects the optical and structural properties of the synthesized QDs. • MPA-capped QDs showed the highest intensity (67%), followed by GSH-capped QDs (22%) and MPA-GSH-capped QDs (19%). • The energy band gap of the synthesized QDs was estimated using the TAUC plots and the DASF method. • MPA-capped QDs demonstrated higher crystallinity and larger crystallite size than GSH-capped QDs and MPA-GSH-capped QDs. In this study, zinc selenide quantum dots (ZnSe QDs) were synthesized using a colloidal method with three stabilizers: 3-mercaptopropionic acid (MPA), glutathione (GSH), and a combination of MPA-GSH. The QDs were analysed using various techniques to understand the impact of the stabilizers on the optical, morphological and structural properties of the synthesized QDs. The results demonstrate that the choice of stabilizer significantly affects the properties of the synthesized QDs. MPA-capped QDs exhibited superior photoluminescence intensity (67%), followed by GSH-capped QDs (22%) and MPA-GSH-capped QDs (19 %). The ultraviolent visible (UV–Vis) absorption spectra reveal different bands for the capping ligands, and the energy band gap for the QDs was evaluated using the TAUC plots and the derivation of the absorption spectrum fitting method (DASF) method. The X-ray diffraction (XRD) patterns indicate that MPA and MPA-GSH-capped QDs demonstrate higher crystallinity, while GSH-capped QDs show some amorphous structures with broad size distribution. The estimated strain and dislocation density indicate that even though the defect density generated inside the crystalline lattice of MPA-capped QDs is high, the internal stress produced was smaller than GSH and MPA–GSH-capped QDs. The scanning electron microscope (SEM) images for MPA-capped QDs show higher mono-dispersity with bigger particle sizes. In contrast, GSH-capped QDs show smaller particle sizes, and MPA-GSH demonstrated particles with mixed morphology. These findings are important as they provide valuable insights into tuning the optical and structural properties of ZnSe QDs, opening new possibilities for their potential applications in optoelectronics and biomedical imaging.