Prenucleation Cluster Effects on Colloidal CdSe Semiconductor Samples in Dispersion at Room Temperature

The possible presence of prenucleation clusters (PNCs) in samples of colloidal semiconductor quantum dots (QDs) remains largely unknown. Using CdSe QDs as a model system, It is shown for the first time that samples from both heating-up and hot-injection approaches may contain the PNC. When a sample is dispersed in cyclohexane (CH) or toluene (Tol) at 25 °C, the nucleation and growth (N/G) of small QDs takes place. In the presence of butylamine (BTA) magic-size clusters (MSCs) develop instead, as evidenced by MSC-390 and MSC-415 (respectively displaying optical absorption peaks at 390 and 415 nm). It is concluded that in dispersion at 25 °C the PNC-monomer-QD and PNC-MSC transformations occur. In the presence of the PNC, the QD growth is in a size-focusing regime. This study provides compelling evidence for the existence of the PNC and for the N/G of II-VI QDs from individual precursors of metal and chalcogenide following the PNC-based pathway.