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摘要
It is not resolved which model describes better the aqueous‐phase nucleation and growth of semiconductor quantum dots (QDs), the classical one‐step one or the nonclassical multi‐step one. Here, we design a room‐temperature reaction to trap reaction intermediates in the prenucleation stage of ZnSe QDs (as a model system). We show that the trapped intermediate can transform to magic‐size clusters (MSCs) via intra‐molecular reorganization and can fragment to enable the growth of QDs. The MSCs exhibit a sharp optical absorption peaking at 299?nm, labelled MSC‐299. The intermediate, the precursor compound (PC‐299) of MSC‐299, is optically transparent at 299?nm and to longer wavelengths. This intermediate forms in various Zn and Se reaction systems. The present study provides unambiguous evidence that the nonclassical and classical pathways are both necessary to explain the nucleation and growth of aqueous‐phase QDs, with the former pathway favored more by high reaction concentrations.(#br)In the prenucleation stage of aqueous‐phase ZnSe quantum dots (QDs), an optically‐transparent intermediate forms, which can transform to absorbing magic‐size clusters (MSC‐299). The MSC precursor compound (PC‐299) fragments passively when a room‐temperature reaction proceeds beyond nucleation, while aggressively at elevated temperatures. High reaction concentrations favor the PC‐299 formation more.
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