Band gap engineering of quaternary-alloyed ZnCdSSe quantum dots via a facile phosphine-free colloidal method.

We demonstrate the synthesis of quaternary-alloyed Zn(x)Cd(1-x)S(y)Se(1-y) quantum dots (ZnCdSSe QQDs) across the entire composition range (x, y) = 0 to 1 with a size tunable from 4.0 to 10.0 nm by a facile, "green", phosphine-free, low-cost colloidal method. The ZnCdSSe QQDs have both composition- and size-dependent band gaps, which can be hybrid-engineered to span the entire visible spectrum. The new ZnCdSSe QQDs are easy to synthesize and have high quantum yields (up to 65%) without the necessity of overcoating a shell. These new quantum dots may find broad uses in biolabeling, biosensing, light-emitting diodes, and other nanodevice applications.