Room temperature synthesis of aqueous ZnCuInS/ZnS quantum dots

In this work a new method was developed for synthesis of aqueous cadmium-free, CuInS (CIS) quantum dots (QDs) at room temperature. CIS QDs as cores were alloyed with 25% of Zn2+ ions at room temperature and followed by the growth of ZnS shell to form CIS and ZCIS QDs. X-ray diffraction (XRD) analysis confirmed that the ZCIS QDs have a wurtzite structure. Moreover, the energy-dispersive X-ray (EDX) analysis demonstrated that ZCIS QDs are composed of Cu, In, Zn and S elements. It was found that Zn ions introduced into CIS QDs lattice structure did not change in the crystal structure. ZCIS/ZnS QDs showed high photoluminescence (PL) peak and its position and intensity depend on the Cu:In ratio. High resolution transmission electron microscope (HRTEM) images showed that ZCIS and ZCIS/ZnS QDs have a spherical shape with average diameter sizes of 4.0 nm and 7.0 nm, respectively. The selected area electron diffraction (SAED) suggested that the prepared ZCIS QDs are crystalline with an interplanar distance of 0.320 nm.