Four Types of CdTe Magic-Size Clusters from One Prenucleation Stage Sample at Room Temperature.

Four types of colloidal semiconductor CdTe magic-size clusters (MSCs), each of which is in a single-ensemble form, have been obtained at room temperature from a single induction period (IP) sample in dispersion. The induction period is the prenucleation stage that occurs prior to nucleation and growth of colloidal quantum dots (QDs). Three types display sharp optical absorption peaking at either 371, 417, or 448 nm, and the fourth type exhibits a sharp absorption doublet with peaks at 350 and 371 nm. These MSCs are respectively denoted as sMSC-371, sMSC-417, sMSC-448, and dMSC-371. We show that the evolution of the various MSCs is affected by the nature of their dispersions. We hypothesize that the evolution of MSCs involves their precursor compounds (PCs), which are transparent in optical absorption. The present study explores new avenues for the exclusive synthesis of four types of CdTe MSCs (with each in a single-ensemble form) and provides an improved understanding for their formation.