Multi-colored type-I Ag-doped ZnCdS/ZnS core/shell quantum dots with intense emission

Abstract

Abstract Although doped quantum dots (d-dots) with intense and tunable emission have been studied for long time, there are still great efforts to prepare new ones with promising characteristics. In the present work, we used a mild/effective strategy for preparing high quality and aqueous-soluble Ag:ZnCdS/ZnS core/shell quantum dots (QDs) with N-acetyl- l -cysteine as the capping agent. Through investigating the experimental variables, the impurity-related emission intensity of the as-prepared samples was optimized. The capability of the present work on creating quantum structures with tunable emission across the entire visible spectrum was approved through simple but effective variation in Zn-to-Cd molar ratio. Indeed, as the Zn:Cd molar ratio changed from 2:0 to 0:2, the emission color was changed significantly from blue to red color with a satisfactory photoluminescence quantum yield. The quantum yield value reached ∼41% for the as-prepared core/shell d-dots without any pre/post-treatment, which is a remarkable result for such aqueous-soluble structures. XRD, EDX, ICP, and TEM measurements were applied to determine the structural features of the QDs in a strong quantum confinement regime. The generality of preparation route, its biocompatibility, along with a multi-color emission, can create new opportunities especially for the white light emitting technologies, or multi-color bioimaging for theranostics.