Nanoparticle Zn 2x Cu 1−x In 1−x S 2 is a promising and safer alternative to lead-and cadmium-containing quantum dots. Students prepare Zn 0.44 Cu 0.78 -In 0.78 S 2 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 Samples are withdrawn from the hot solution and quenched at room temperature to produce a series of increasing nanoparticle sizes with the same chemical composition.