Room-Temperature Evolution of Ternary CdTeS Magic-Size Clusters Exhibiting Sharp Absorption Peaking at 381 nm

Abstract

Colloidal semiconductor ternary CdTeS magic-size clusters (MSCs) have not been reported. Here, we present the first synthesis of CdTeS MSCs at room temperature and our understanding of the evolution pathway. The MSCs exhibit sharp optical absorption peaking at 381 nm and are labeled MSC-381. CdTeS MSC-381 evolves when pre-nucleation-stage samples of binary CdTe and CdS that do not contain quantum dots (QDs) are separately prepared and then mixed and incubated at room temperature. We propose that CdTeS MSC-381 evolves from its precursor compound (PC) via quasi-isomerization. Synchrotron-based small-angle X-ray scattering suggests that PCs/MSCs of CdTe and CdTeS are similar in sizes. We propose further that the CdTeS PC forms from the substitution reaction between the CdTe PC and the CdS monomer/fragment (Mo/Fr). The present study paves the way to the room-temperature evolution of ternary MSCs and provides an in-depth understanding of the PC to MSC transformation.

Transformations of Magic-Size Clusters via Precursor Compound Cation Exchange at Room Temperature

“…In addition to the present CE reaction, we have demonstrated that the binary ME PC can experience another four chemical reactions. They are isomerization to binary ME MSCs, − ,− ,,, substitution reactions followed by isomerization to binary or ternary MSCs (Figure S1B), ,− ,, addition reactions followed by isomerization to photoluminescent MSCs (Figure S1B), and fragmentation to QDs. , For the reaction of M and E precursors to ME QDs, the E precursor dominates the self-assembly of the M and E precursors that results in the formation of the ME PC with similar stoichiometry. The present finding of the E-dominated, magic self-assembly principle, together with the recent discovery of these binary and ternary MSCs and the successful synthesis of small-size QDs with enhanced yield, demonstrates that we are able to push further “chemical self-assembly” …”

“…In addition to the present CE reaction, we have demonstrated that the binary ME PC can experience another four chemical reactions. They are isomerization to binary ME MSCs, [2][3][4][5][14][15][16]18,34,35 substitution reactions followed by isomerization to binary or ternary MSCs (Figure S1B), 17,[34][35][36][37]53,54 addition reactions followed by isomerization to photoluminescent MSCs (Figure S1B), 55 and fragmentation to QDs. 2,56 For the reaction of M and E precursors to ME QDs, the E precursor dominates the selfassembly of the M and E precursors that results in the formation of the ME PC with similar stoichiometry.…”

Direct and Indirect Pathways of CdTeSe Magic-Size Cluster Isomerization Induced by Surface Ligands at Room Temperature

“…The concentrations of MSC-399 and PhOH in Figure a are similar to those shown in the Figure NMR study (sample 1) and in the study in Figures –. When process variables (including the nature of the incoming ligand) and the pathway that govern the isomerization of MSCs are understood, we will be in a stronger position to fully manipulate MSC isomerization and to better control their physicochemical properties. , Also, the knowledge about the surface ligand chemistry will enable our synthetic capability, ,− and the MSC isomerization pathway provides valuable information for the isomerization of ME clusters, together with organic molecules (Figure S1.1) and metal clusters. ,,− …”

“…The discrete pattern of the spectrum change usually displays a characteristic isosbestic point located between the two absorption peaks of MSC-1 and MSC-2, without intermediate absorptions. MSCs have their precursor compounds (PC), ,− and the isomerization pathway is modeled as going through their PCs. ,,, That is from MSC-1 to PC-1, then to PC-2, and finally to MSC-2. Being relatively optically transparent, the PCs do not absorb at the peak position of their counterpart MSCs or to longer wavelengths.…”

Enhanced Reactivity of Magic-Sized Inorganic Clusters by Engineering the Surface Ligand Networks

“…Kim et al elucidated the role of the InAs-cluster-based SSP in synthesizing large InAs QDs (>9 nm) . A two-step nucleation of group II–VI MSCs (e.g., CdS) was reported, in which, under certain conditions, MSC pre-nucleation clusters (named precursor compounds or PCs) first formed and transformed into MSCs of a similar core composition. − It was shown that the fragmentation of CdS PCs leads to the nucleation and growth of small-size CdS QDs with enhanced particle yield …”