Prof. Qui Yu’s research team of the Engineering Research Center in Biomaterials/Institute of Atomic and Molecular Physics,Sichuan University has recently published inAngewandte Chemie International Editionresearch findings regarding the formation and evolution of prenucleation clusters titled "Thermally Induced Isomerization of Prenucleation Clusters During the Prenucleation Stage of CdTe Quantum Dots". Sichuan University is listed as the work unit of the paper. The two first authors are Tinghui Wang and Dr. Zhe Wang, and Kui Yu and Dr. Chaoran Luan are the co corresponding authors.
The team proposed that the nucleation and growth of colloidal semiconductor QD follow a non-classical multi-step nucleation pathway model. Before nucleation, II-VI metal (M) and sulfur group (E) precursor compounds are generated in micelles through self-assembly and M-E covalent bonding, forming relatively disordered clusters arranged in atomic space.
“The evolution of prenucleation clusters in the prenucleation stage of colloidal semiconductor quantum dots (QDs) has remained unexplored. With CdTe as a model system, we show that substances form and isomerize prior to the nucleation and growth of QDs. Called precursor compounds (PCs), the prenucleation clusters are relatively optically transparent and can transform to absorbing magic-size clusters (MSCs). When a prenucleation-stage sample at 25, 45, or 80 °C is dispersed in a mixture of cyclohexane (CH) and octylamine (OTA) at room temperature, either MSC-371, MSC-417, or MSC-448 evolves with absorption peaking at 371, 417, or 448 nm, respectively. We propose that PC-371 forms at 25 °C, and isomerizes to PC-417 at 45 °C and to PC-448 at 80 °C. The PCs and MSCs are quasi isomers. Relatively large and small amounts of OTA favor PC-371 and PC-448 in dispersion, respectively. The present findings suggest the existence of PC-to-PC isomerization in the QD prenucleation stage.” (Abstract)
This seminal research achievement has promoted the precise construction of clusters and laid a new scientific foundation for the material synthesis of QD.
Fig. 1.In the prenucleation stage of colloidal semiconductor CdTe quantum dots (QDs), precursor compounds (PCs) of magic-size clusters (MSCs) form and isomerize. When the reaction temperature is increased, PC-371 forms at 25 °C and isomerizes to PC-448 at 80 °C via PC-417 at 45 °C. When a prenucleation-stage sample is placed in a mixture of cyclohexane (CH) and octylamine (OTA), the PCs that have formed transform quickly to their counterpart MSCs.