Synthesis of Multifunctional Mn‐Doped CdTe/ZnS Core/Shell Quantum Dots

Abstract

The synthesis of a novel water-soluble Mn-doped CdTe/ZnS core-shell quantum dots using a proposed ultrasonic assistant method and 3-mercaptopropionic acid (MPA) as stabilizer is descried. To obtain a high luminescent intensity, post-preparative treatments, including the pH value, reaction temperature, reflux time and atmosphere, have been investigated. For an excellent fluorescence of Mn-doped CdTe/ZnS, the optimal conditions were pH 11, reflux temperature 100 and reflux time 3 h under N ℃ 2 atmosphere. While for phosphorescent Mn-doped CdTe/ZnS QDs, the synthesis at pH 11, reflux temperature 100 ℃ and reflux time 3 h under air atmosphere gave the best strong phosphorescence. The characterizations of Mn-doped CdTe/ZnS QDs were also identified using AFM, IR, powder XRD and thermogravimetric analysis. The data indicated that the photochemical stability and the photoluminescence of CdTe QDs are greatly enhanced by the outer inorganic ZnS shell, and the doping Mn 2＋ ions in the as-prepared quantum dots contribute to strong luminescence. The strong luminescence of Mn-doped CdTe/ZnS QDs reflected that Mn ions act as recombination centers for the excited electron-hole pairs, attributing to the transition from the triplet state ( 4 T 1 ) to the ground state ( 6 A 1 ) of the Mn 2＋ ions. All the experiments demonstrated that the surface states played important roles in the optical properties of Mn-doped CdTe/ZnS core-shell quantum dots.

One-Pot Aqueous Phase Synthesis of CdTe and CdTe/ZnS Core/Shell Quantum Dots

“…What's more, using tellurium powder as the Te source should be freshly reduced by sodium borohydride before synthesis process, which takes long time (>6 h) to be dissolved in ice bath even under ultrasonication (>1 h). 17 , it is important and inevitable to explore a simple, rapid and economical method for large scale production with excellent optical properties and stability. However, the bare semiconductor nanocrystals have tremendous limitations 22 like photoinduced decomposition, conjugate aggregation, rapid photobleaching and biotoxicity, which mainly relate to their instable surface states such as dangling uncoordinated bonds and surface defects. Therefore, a strategy to cap the QDs using organic passivating layers or inorganic capping ligands 23 has been proposed to protect QDs.…”