Aqueous synthesis of highly fluorescent and color-tunable Ag + -doped Cd x Zn 1-x S quantum dots
Résumé
Facile and low cost syntheses of 3-mercaptopropionic acid-capped Ag:CdxZn1-xS and of core/shell Ag:CdxZn1-xS/ZnS quantum dots (QDs) are presented. The effects of the Ag+ doping concentration and of the Cd/Zn ratio on the structural and optical properties of the dots were investigated. Core Ag:CdxZn1-xS QDs have an average diameter of ca. 4.5 nm and their photoluminescence (PL) emission can be tuned from 478 to 610 nm by varying the dopant concentration or the composition of the CdxZn1-xS host material. The highest PL quantum yield (25%) is obtained when using 2 or 3.5% doping in Ag+. The PL quantum yield increased substantially (44%) after capping the Ag:CdxZn1-xS core with a ZnS shell. Due to their high photostability and long excited-state lifetimes (1–2 μs), Ag:CdxZn1-xS QDs are of high potential as nanophosphors or as fluorescent probes for bio-imaging.