Synthesizing and Investigating Photoluminescence Properties of CdTe and CdTe@CdS Core-Shell Quantum Dots (QDs): A New and Simple Microwave Activated Approach for Growth of CdS Shell Around CdTe Core

In this work, photoluminescence (PL) properties of CdTe and CdTe@CdS core-shell quantum dots (QDs) were investigated. CdTe and CdTe@CdS QDs were synthesized using a microwave activated method. CdS shell grown using a microwave activated method which was based on the heat sensitivity of Na2S2O3. X-ray diffraction (XRD) analysis demonstrated cubic crystalline structure for both of the synthesized QDs, but for CdTe@CdS QDs, XRD diffraction peaks shifted to the longer angle. Sizes of CdTe and CdTe@CdS QDs were obtained as about 2.5 and 3.5 nm from transmission electron microscopy (TEM) images. UV-Vis and PL spectra showed that in this method both of the absorption and emission of CdTe QDs shifted from near blue to near red. By the growth of CdS shell around CdTe QDs, a red shift was observed in absorption and PL spectra. PL QY was obtained as about 23% and 38% for CdTe and CdTe@CdS core-shell QDs, respectively. Increase in the thickness of the CdS shell was possible only by the increase in the microwave irradiation time in the CdS shell growth step. Growth of the CdS shell around CdTe core, resulted in the red shift in band edge and PL spectra to the longer wavelengths.