CdSe and CdSe/CdS core-shell QDs: New approach for synthesis, investigating optical properties and application in pollutant degradation.

In this work, CdSe quantum dots (QDs) were synthesized by a simple and rapid microwave activated approach using CdSO4 , Na2 SeO3 as precursors and thioglycolic acid (TGA) as capping agent molecule. A novel photochemical approach was introduced for the growth of CdS QDs and this approach was used to grow a CdS shell around CdSe cores for the formation of a CdSe/CdS core-shell structure. The core-shells were structurally verified using X-ray diffraction, transmission electron microscopy and FTIR (Fourier-transform infrared (FTIR)) spectroscopy. The optical properties of the samples were examined by means of UV-Vis and photoluminescence (PL) spectroscopy. It was found that CdS QDs emit a broad band white luminescence between 400 to 700 nm with a peak located at about 510 nm. CdSe QDs emission contained a broad band resulting from trap states between 450 to 800 nm with a peak located at 600 nm. After CdS shell growth, trap states emission was considerably quenched and a near band edge emission was appeared about 480 nm. Optical studies revealed that the core-shell QDs possess strong ultraviolet (UV) - visible light photocatalytic activity. CdSe/CdS core-shell QDs, showed an enhancement in photodegradation of Methyl orange (MO) compared with CdSe QDs.