Synthesis and Analysis of Zinc Copper Indium Sulfide Quantum Dot Nanoparticles

Nanoparticle Zn2x Cu1–x ­In1–x S2 is a promising and safer alternative to lead- and cadmium-containing quantum dots. Students prepare Zn0.44Cu0.78­In0.78S2 quantum dots in a one-pot synthesis without an inert atmosphere and investigate how the color, visible absorption band edge, and photoluminescence peak wavelength depend on the size of the particle. Octadecene is used as a noncoordinating solvent with a high boiling point. Oleic acid and stearic acid are used as ligands to dissolve the metal salts in the solvent at ∼150 °C. Dodecanethiolate coordinates to the metal ion, and above 200 °C, the metal thiolate decomposes to produce metal sulfide nanoparticles, coated in dodecanethiolate. Samples are withdrawn from the hot solution and quenched at room temperature to produce a series of increasing nanoparticle sizes with the same chemical composition.