Formation of highly luminescent Zn1−xCdxSe nanocrystals using CdSe and ZnSe seeds

High-quality colloidal Zn1−xCdxSe nanocrystals (NCs) with tunable photoluminescence (PL) from blue to orange were synthesized using oleic acid as a capping agent. The Zn1−xCdxSe NCs were prepared through two approaches: using CdSe or ZnSe seeds. In the case of CdSe NCs as seeds, Zn1−xCdxSe NCs were fabricated by the reaction of Zn, Cd, and Se precursors in the coordinating solvent system at high temperature. The Zn1−xCdxSe NCs revealed orange emitting. A significant blue-shift of absorption and PL spectra were observed with time, indicating the formation of ternary NCs. In contrast, Zn1−xCdxSe NCs revealed blue to green PL for ZnSe NCs as seeds. This is ascribed to an embryonic nuclei-induced alloying process. With increasing time, the Zn1−xCdxSe NCs exhibited a red-shift both in their absorption and PL spectra. This is attributed to the engineering in band gap energy via the control of NC composition. The PL properties of as-prepared alloyed NCs are comparable or even better than those for the parent binary systems. The PL peak wavelength of the Zn1−xCdxSe NCs depended strongly on reaction time and the molar ratio of Cd/Zn. The Zn1−xCdxSe NCs revealed a spherical morphology and exhibited a wurtzite structure according to transmission electron microscopy observation and an X-ray diffraction analysis.

► High-quality Zn1−xCdxSe nanocrystals (NCs) were fabricated through a step synthesis. ► The alloy structure of the NCs depended strongly on preparation procedures. ► CdSe or ZnSe cores created in the NCs due to different growth kinetics. ► The CdSe and ZnSe cores in the NCs affected photoluminescence properties of theNCs.