Reversible Facet Reconstruction of CdSe/CdS Core/Shell Nanocrystals by Facet–Ligand Pairing

Lei, Hairui; Li, Tenghui; Li, Jiongzhao; Zhu, Jie; Zhang, Haibing; Qin, Haiyan; Kong, Xueqian; Wang, Linjun; Peng, Xiaogang

doi:10.1021/jacs.2c13500

Cited by 17 publications

(42 citation statements)

References 79 publications

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“…Consequently, wurtzite nanocrystals with various shapes may be synthesized by fine-tuning the ligand system. For instance, formation of CdSe@CdS dot@platelet nanocrystals with the negatively charged (000) and positively charged (0001) facets as the basal planes would always require a mixed ligand system of fatty amines (in the form of ammonium ions) and cadmium alkanoates with a relatively high concentration of amines. ,,, By reducing the relative concentration of fatty amines, pyramidal (or rod-shape) CdSe/CdS core/shell nanocrystals would be the preferential products, which are elongated along the (0001) direction and have sharp tip(s) at the (000) direction. , …”

Section: Crystal Facet and Synthetic Implicationsmentioning

confidence: 99%

“…The section above illustrates that, at an atomic level, lattice bonding and charging of the surface sites are diverse and facet-dependent. In principle, surface atomic sites should be matched by the surface ligands in terms of lattice coordination, charging, and steric environment, which is known as facet–ligands pairing . This is distinctively different from the formation of a typical complex by a given set of ligands and metal ions in solution, and thus the conventional Green’s classification of ligands bonding modes (X-type, Z-type, and L-type) is unlikely to be suited for describing bonding modes for nanocrystal-ligands complexes.…”

Section: Inorganic–ligands Interface and Facet–ligands Pairingmentioning

confidence: 99%

“…As pointed out above, there is barely any tool that could directly and unambiguously offer an atomic–molecular level picture for the nanocrystal surface, which is still true when we narrow our attention down to the inorganic-ligands interface. At present, a practical way to bypass this challenge is to combine advanced spectroscopic and microscopic measurements with density functional theory (DFT) calculations, ,− ,, provided that nanocrystals with well-defined facets are available. However, DFT calculations are usually looking for local minimum(s) within the initially chosen system, and thus to make DFT calculations meaningful, several guidelines should be considered. The solution system for the formation of facet-controlled nanocrystals should be as defined as possible.…”

Section: Inorganic–ligands Interface and Facet–ligands Pairingmentioning

confidence: 99%

“…(c) Facet−ligands pairing of low-index facets of CdSe (or CdS) nanocrystals and alkanoate ligands. [Reproduced with permission from refs and . Copyright 2019 and 2023, American Chemical Society, Washington, DC.…”

Section: Inorganic–ligands Interface and Facet–ligands Pairingmentioning

confidence: 99%

“…Strictly speaking, there is no characterization tool that can directly provide a complete picture of the surface of a typical spheroidal nanocrystal at an atomic-molecular level . However, by coupling advanced experimental tools and theoretical calculations, ,− this problem can be addressed by dividing it to three spatial zones, worthy to be discussed.…”

Section: Introductionmentioning

confidence: 99%

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Toward Surface Chemistry of Semiconductor Nanocrystals at an Atomic-Molecular Level

Lei

Kong

et al. 2023

Acc. Chem. Res.

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Conspectus Properties of colloidal semiconductor nanocrystals with a single-crystalline structure are largely dominated by their surface structure at an atomic-molecular level, which is not well understood and controlled, due to a lack of experimental tools. However, if viewing the nanocrystal surface as three relatively independent spatial zones (i.e., crystal facets, inorganic−ligands interface, and ligands monolayer), we may approach an atomic-molecular level by coupling advanced experimental techniques and theoretical calculations. Semiconductor nanocrystals of interest are mainly based on compound semiconductors and mostly in two (or related) crystal structures, namely zinc-blende and wurtzite, which results in a small group of common low-index crystal facets. These low-index facets, from a surface-chemistry perspective, can be further classified into polar and nonpolar ones. Albeit far from being successful, the controlled formation of either polar or nonpolar facets is available for cadmium chalcogenide nanocrystals. Such facet-controlled systems offer a reliable basis for studying the inorganic–ligands interface. For convenience, here facet-controlled nanocrystals refer to a special class of shape-controlled ones, in which shape control is at an atomic level, instead of those with poorly defined facets (e.g., typical spheroids, nanorods, etc). Experimental and theoretical results reveal that type and bonding mode of surface ligands on nanocrystals is facet-specific and often beyond Green’s classification (X-type, Z-type, and L-type). For instance, alkylamines bond strongly to the anion-terminated (000) wurtzite facet in the form of ammonium ions, with three hydrogens of an ammonium ion bonding to three adjacent surface anion sites. With theoretically assessable experimental data, facet−ligands pairing can be identified using density functional theory (DFT) calculations. To make the pairing meaningful, possible forms of all potential ligands in the system need to be examined systematically, revealing the advantage of simple solution systems. Unlike the other two spatial zones, the ligands monolayer is disordered and dynamic at an atomic level. Thus, an understanding of the ligands monolayer on a molecular scale is sufficient for many cases. For colloidal nanocrystals stably coordinated with surface ligands, their solution properties are dictated by the ligands monolayer. Experimental and theoretical results reveal that solubility of a nanocrystal–ligands complex is an interplay between the intramolecular entropy of the ligands monolayer and intermolecular interactions of the ligands/nanocrystals. By introducing entropic ligands, solubility of nanocrystal-ligands complexes can be universally boosted by several orders of magnitude, i.e., up to >1 g/mL in typical organic solvents. Molecular environment in the pseudophase surrounding each nanocrystal plays a critical role in its chemical, photochemical, and photophysical properties. For some cases, such as the synthesis of high-quality nanocrystals, all three...

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