Synthesis of Fluorescent CdS Quantum Dots of Tunable Light Emission with a New in Situ Produced Capping Agent

Herein, we report an ambient synthesis of CdS QDs with widely tunable particle size by sulfur source of H 2 S and a new capping agent R-2-thiotetrahydrothiazole-4-carboxylic acid in situ produced from the reaction of l -cysteine with carbon disulfide in water. XRD, FTIR, UV–vis, PL, and TEM measurements were used to characterize the synthesized CdS QDs. Small particle size in a range of 1–3 nm and five PL colors from dark, deep blue to yellow of CdS QDs were achieved by changing the molar ratio and pH value of preparation. These CdS colloid solutions exhibit high stability even under weak acidity conditions at pH 6.5. The CdS QDs display highest emission intensity at a concentration of 2 mM.