Facile Synthesis of Ternary Alloy of CdSe_1-<em>x</em>S<em>_x</em> Quantum Dots with Tunable Absorption and Emission of Visible Light

The synthesis of alloyed semiconductor quantum dots has produced structures that have distinct properties in comparison with both their bulk counterparts and their parent binary semiconductor quantum dots. In this work, the quantum confined structures of a ternary alloy of CdSe_1−<i>x</i>S<i>_x</i> were synthesized by one-pot synthesis method in an aqueous medium at a low temperature and capped with 3-mercaptopropoionic acid. Structures of the synthesized quantum dots were investigated by energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The obtained quantum dots had modified cubic structures as proven by X-ray diffraction and selected area electron diffraction. The optical properties of the synthesized quantum dots were characterized by optical absorption, photoluminescence, and color analysis. Optical absorption investigation revealed a widening of the band gap of CdSe_1−<i>x</i>S<i>_x</i> with increasing S content. This widening increased for the samples suspended in water relative to the samples measured in powder form due to the difference in the environment of the two cases. The size determined from the optical absorption measurements was found to be compatible with the sizes obtained from the X-ray diffraction with the value of bowing parameter around 1, which indicated a graded diffusion of sulfur. It was also ascertained that the emission of different compositions covered the most visible range with a small full width at half maximum. The <i>x</i> and <i>y</i> values of the chromaticity coordinates decreased with increasing sulfur content of up to 15%, while the <i>z</i> value increased.