Scalable single-step noninjection synthesis of high-quality core/shell quantum dots with emission tunable from violet to near infrared.

The common two-step "hot-injection" methods are not suitable for reproducible production of core/shell quantum dots (QDs) at large scale for practical applications. Herein we develop a scalable, reproducible, and low-cost synthetic approach for high-quality core/shell QDs (CdS/Zn(x)Cd(1-x)S, CdSe/Zn(x)Cd(1-x)S, and CdTe/Zn(x)Cd(1-x)S) with shell material composed of gradient alloy structure by directly heating commercial available, air-stable CdO, Zn(NO(3))(2), and chalcogenide elements in octadecene media at air. With simple variation of reaction recipe (reactants and feeding ratio), luminescence color of the resulting QDs can be conveniently tuned from violet to near-infrared (400-820 nm). The emission efficiency of the as-prepared QDs can be up to 80%. Moreover, the high emission efficiency can be preserved after QDs transferred into aqueous media via ligand exchange. The structure, chemical composition, and optical properties of the obtained QDs have been characterized with use of transmission electron microscopy, elemental analysis, and optical spectroscopy. The scalability of the reported approach has been demonstrated by the facile preparation of gram-scaled QD product in one batch reaction.