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Synthesis of White Light Emitting Water-soluble CdZnS Quantum Dots at Room Temperature

Abhijit Mandal

Abstract


Water-soluble alloyed CdZnS quantum dots (QDs) have been successfully prepared at room temperatures by reacting a mixture of Cd(CH3COO)2 and Zn(CH3COO)2 with Na2S using thiolactic acid (TLA) as a surface capping agent. The photoluminescence (PL) spectra of the alloyed QDs are determined on the basis of the Cd2+/Zn2+ molar ratio, reaction pH, intrinsic Cd2+and Zn2+reactivities toward Na2S and the concentration of capping agent. A systematic blue shift in emission wavelength of the alloyed QDs was found with the increase in Zn precursor concentration. This gives clear evidence of the formation of CdZnS alloy QDs by the simultaneous reaction of Cd2+ and Zn2+with Na2S, rather than the formation of separate CdS and ZnS QDs or core-shell structure CdS/ZnS type QDs. The size and morphology of these synthesized QDs are determined by using high-resolution transmission electron microscopy. These QDs exhibited excellent colloidal and photostability over a span of years and showed intense white photoluminescence which could be suitable for luminescent solar concentrators, LEDs, and bio-imaging. The water-soluble TLA capped CdZnS QDs synthesized
in our laboratory offer unique advantages including one-step synthesis, tunable white-light emission, and room temperature requirement.


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