Role of synthesis conditions in the power-dependent fluorescence intermittency of CuInS2 /ZnSeS quantum dots: Injection vs one-pot shelling

by Kaur, Harneet; Heyes, Colin D.

Colloidal semiconductor nanocrystals, also called quantum dots (QDs), possess size-tunable photoluminescence and high optical stability which offers great potential applications of these nanocrystals in bioimaging, solar-harvesting materials, and lasers. CuInS2 quantum dots are non-toxic alternatives to the more common CdSe-based quantum dots. As is the case for CdSe, shelling CuInS2 improves these optical properties. However, unlike shelling CdSe, CuInS2 tend to undergo significant ion exchange during this step leading to a large degree of alloying, which complicates the structural-optical property relationships. A particularly interesting property is fluorescence intermittency, also known as blinking, which can limit these nanocrystals' optoelectronic and biol. applications and control over this phenomenon is essential to their eventual application.In the literature, two different approaches to shelling have been reported; hot injection and one-pot. In the simpler one-pot approach, all shelling precursors are added at room temperature and the mixture is heated to the reaction temperature In the more complicated hot injection approach, the CuInS2 cores are heated to the reaction temperature and the shelling precursors are slowly added. These two different approaches could lead to different quantum dot architectures that may affect their optical properties. In this study, we compare the power-dependence of blinking of CuInS2 /ZnSeS that have been synthesized using each of these approaches to determine how the synthesis conditions affect the quantum dots' structure and resulting single particle optical properties.