Room-Temperature Interconversion Between Ultrathin CdTe Magic-Size Nanowires Induced by Ligand Shell Dynamics

Abstract

The formation mechanisms of colloidal magic-size semiconductor nanostructures have remained obscure. Herein, we report the room temperature synthesis of three species of ultrathin CdTe magic-size nanowires (MSNWs) with diameters of 0.7 ± 0.1 nm, 0.9 ± 0.2 nm, and 1.1 ± 0.2 nm, and lowest energy exciton transitions at 373, 418, and 450 nm, respectively. The MSNWs are obtained from Cd(oleate) 2 and TOP-Te, provided diphenylphosphine and a primary alkylamine (RNH 2 ) are present at sufficiently high concentrations, and exhibit sequential, discontinuous growth. The population of each MSNW species is entirely determined by the RNH 2 concentration [RNH 2 ] so that single species are only obtained at specific concentrations, while mixtures are obtained at concentrations intermediate between the specific ones. Moreover, the MSNWs remain responsive to [RNH 2 ], interconverting from thinner to thicker upon [RNH 2 ] decrease and from thicker to thinner upon [RNH 2 ] increase. Our results allow us to propose a mechanism for the formation and interconversion of CdTe MSNWs and demonstrate that primary alkylamines play crucial roles in all four elementary kinetic steps (viz., monomer formation, nucleation, growth in length, and interconversion between species), thus being the decisive element in the creation of a reaction pathway that leads exclusively to CdTe MSNWs. The insights provided by our work thus contribute toward unravelling the mechanisms behind the formation of shape-controlled and atomically precise magic-size semiconductor nanostructures.

Formation and Transformation of ZnTe and CdTe Magic-Size Clusters Assisted by Their Precursor Compounds

“…The PC-assisted MSC transformations display a stepwise spectral shift pattern in optical absorption. − ,,,− When the shift has a continuous pattern instead, the mother cluster transforms directly (Figure S5-6). , How 0D MSCs, − ,− ,,− 0D QDs, ,,,− 1D nanowires, − and 2D nanoplatelets evolve remains controversial in expert circles (Figures S5-7 and S5-8), − ,,,− together with MSC compositions (Figures S4-5–S4-7). ,,, Hopefully, the concept of the extreme quantum confinement (Scheme S5) will provide a theoretical understanding for the MSC transformations. , …”

“… ,− , The present study paves the way to synthesizing PL CdTe MSC-481 that is free of CdTe QDs, possibly facilitating potential applications in optoelectronic devices and photocatalysis. , The PC-related new concepts (including those shown in Schemes S1–S4) about the formation and transformation of MSCs are developed based on experimental evidence. Analogous to the development of macromolecular science that was enabled after the concept was accepted that polymers consist of monomeric units linked by covalent bonds and thus are high molecular weights, , these PC-related new principles will promote a rational and systematic (rather than purely empirical) development of semiconductor functional nanomaterials and will simulate a fundamental revision of long-standing, well-established but perhaps inadequate concepts, including the idea that changes can only occur directly on mother nanospecies. − ,− The PC-related new chemical concepts presented here are advancing nanosynthetic chemistry. These novel paradigms reflect some of the significant differences between nanosynthetic chemistry and the more traditional organic and inorganic synthetic chemistries.…”

Layer-Structured Anisotropic Metal Chalcogenides: Recent Advances in Synthesis, Modulation, and Applications

“…In recent decades, 1D and 2D anisotropic magic-size clusters (MSCs) have been intensively studied. − The term “magic-size cluster” is used to denote atomically precise clusters of semiconductors with a well-defined number of atoms . MSCs tend to grow in a discontinuous and quantized manner, where MSCs with one magic size grow to the next without intermediate sizes.…”