Facile synthesis of CuInS_2/ZnS quantum dots with highly near-infrared photoluminescence via phosphor-free process

摘要

We present the synthesis of CuInS_2 quantum dots (QDs) with a size range of 3-4 nm through a phosphor-free method. The photoluminescence (PL) properties of CuInS_2 QDs synthesized using various Cu/In molar ratios were investigated. With the decrease of Cu/In molar ratio, the PL peak wavelength revealed a clear blue shift by ca. 100 nm and a noticeable increase in PL intensity. Being coated with a ZnS shell on CuInS_2 QDs, the resulting core/shell QDs exhibited a dramatic increase of PL efficiency and stability, with the maximum PL efficiency up to 39 . This is ascribed to the efficient reduction of non-radiative recombination after surface modification. In addition, the PL peak wavelengths were tuned from 670 to 800 nm. The transmission electron microscopy observation and X-ray diffraction analysis indicated that the CuInS_2 and CuInS_2/ZnS QDs revealed a "dot" shaped morphology and exhibited a wurtzite structure. Time-resolved fluorescence spectroscopy revealed that CuInS_2/ZnS core/shell QDs apparently exhibited a slow decay compared with the CuInS _2 cores (214 ns for CuInS_2/ZnS QDs and 172 ns for CuInS_2 cores). Because of the tunable near-infrared range emission, high stability and long lifetimes of the CuInS_2/ZnS QDs, they will be very useful in applications such as solar cell and biological imaging.