CdTe/CdS Core-Shell Quantum Dots: Synthesis and Applications as a Heavy Metal Ion's Fluorescence Sensor and Photocatalyst for Photodegradation of Organic Dyes

Herein, a simple method for the growth of the CdS shell around CdTe QDs and the formation of the CdTe/CdS core-shell structure is proposed. The synthesized QDs are characterized using Raman, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), and UV-vis analyses. XRD patterns confirm the formation of a core-shell-type structure and particle sizes, lattice strain (epsilon), and displacement density (delta) are calculated using Williamson-Hall (W-H) and Williamson-Smallman (W-S) approaches. Obtained results show that the CdTe/CdS QDs are spherical with an average crystal size about 5.41 nm. In this work, derivation of absorption spectrum fitting (DASF) is used for the determination of the optical bandgap of the prepared QDs. Prepared CdTe/CdS QDs are applied for the detection of the heavy metal ions and photodegradation of the different organic dyes in aqueous media. The prepared QDs show good performance for the detection of mercury ions (Hg2+) in water with superior selectivity and for photodegradation of the methylene orange (MO) under UV light. The comparison of the obtained results for CdTe/CdS with bare CdTe QDs shows that the core-shell CdTe/CdS QDs have higher sensitivity and enhanced photocatalyst properties compared to the CdTe QDs.