Probing intermediates of the induction period prior to nucleation and growth of semiconductor quantum dots

Liu, Mingyang; Wang, Kun; Wang, Linxi; Han, Shuo; Fan, Hongsong; Rowell, N. L.; Ripmeester, John A.; Renoud, Romain; Bian, Fenggang; Zeng, Jianrong; Yu, Kui

doi:10.1038/ncomms15467

Cited by 101 publications

(327 citation statements)

References 80 publications

(216 reference statements)

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“…The relation between CdS MSC−311 and RQDs in the current study is similar to that proposed for CdTe MSC−371 and RQDs. 46 We also explored the formation of IP311 with MALDI-TOF MS, as shown in Figure S5.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Two-Step Nucleation of CdS Magic-Size Nanocluster MSC–311

et al. 2017

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Nucleation has been generally acknowledged as a rapid but uncontrollable process that is difficult to decouple from the subsequent growth phase. Here, we report our finding that nucleation of semiconductor magic-size clusters (MSCs) can be well-regulated, without a subsequent evolution in size. Colloidal semiconductor CdS MSCs were synthesized by a two-step approach intentionally designed, without the simultaneous formation of nanocrystals of other sizes. The nuclei MSCs exhibit a sharp optical absorption peaking at 311 nm and are thus denoted by MSC−311. We prepared the immediate precursor for MSC−311 denoted by IP311 which is liquid-like, through a reaction which was normally performed to grow CdS conventional quantum dots (QDs), but at a different temperature (180°C) prior to the nucleation and growth of CdS QDs. We demonstrate that the nucleation of MSC−311 from IP311 followed first order kinetics remarkably well, and the presence of a small amount of methanol accelerated this process effectively. Moreover, the liquid-like prenucleation cluster IP311 and the nuclei MSC−311 have similar masses. Accordingly, we propose that the intramolecular reorganization of IP311 results in the nuclei MSC−311, the formation of which features a two-step nucleation pathway. The present study introduces methodology via absorption spectroscopy to monitor the nucleation kinetics of semiconductor MSCs from their immediate precursors. The repeatable, predictable, and controllable nucleation process investigated here brings a deeper insight into nucleation of other semiconductor nanocrystals and contributes to the foundation for the future development of advanced theoretical models for crystal nucleation.

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Section: ■ Results and Discussionmentioning

confidence: 99%

“…31 The definition of monomers (such as Cd 1 S 1 or Cd 2 S 2 ) can be found elsewhere. 40−45 Very recently, 46 a study was conducted on the induction period prior to nucleation and growth of cadmium telluride (CdTe) RQDs. This study suggested that CdTe MSC precursors were formed in the induction period.…”

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Two-Step Nucleation of CdS Magic-Size Nanocluster MSC–311

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“…Manipulating functional materials at atom-by-atom basis represents the most ambitious dream of scientists in nanochemistry 1 – 6 . Such dream should be rooted in precise understanding on growth mechanism of nanoparticles (NPs) at atomic level, which has puzzled nanoscience research community for decades, but little has been unraveled so far 7 , 8 . Fundamental breakthrough on particle growth mechanism may come with the recently discovered molecular-like metal NPs.…”

Section: Introductionmentioning

confidence: 99%

Revealing isoelectronic size conversion dynamics of metal nanoclusters by a noncrystallization approach

et al. 2018

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Atom-by-atom engineering of nanomaterials requires atomic-level knowledge of the size evolution mechanism of nanoparticles, which remains one of the greatest mysteries in nanochemistry. Here we reveal atomic-level dynamics of size evolution reaction of molecular-like nanoparticles, i.e., nanoclusters (NCs) by delicate mass spectrometry (MS) analyses. The model size-conversion reaction is [Au23(SR)16]− → [Au25(SR)18]− (SR = thiolate ligand). We demonstrate that such isoelectronic (valence electron count is 8 in both NCs) size-conversion occurs by a surface-motif-exchange-induced symmetry-breaking core structure transformation mechanism, surfacing as a definitive reaction of [Au23(SR)16]− + 2 [Au2(SR)3]− → [Au25(SR)18]− + 2 [Au(SR)2]−. The detailed tandem MS analyses further suggest the bond susceptibility hierarchies in feed and final Au NCs, shedding mechanistic light on cluster reaction dynamics at atomic level. The MS-based mechanistic approach developed in this study also opens a complementary avenue to X-ray crystallography to reveal size evolution kinetics and dynamics.

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“…For example, the pathway from the early phase separation of atoms, ions, or molecules from solutions to the nanoparticle formation is still unclear . Toward filling this gap, multiple‐step models have been recently proposed, which emphasize the presences of several intermediate states prior to nucleation, such as amorphous precursors,[5c,6] magic‐size clusters, condensed liquid phase, prenucleation clusters, etc. Although it is suggested that the energetic barrier for multistep nucleation via intermediate states is lower than that expected in a classical nucleation picture, debates remain due to the lack of direct experimental evidence for early crystallization.…”

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“…Although it is suggested that the energetic barrier for multistep nucleation via intermediate states is lower than that expected in a classical nucleation picture, debates remain due to the lack of direct experimental evidence for early crystallization. [4b,5a,c,7,11]…”

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Revealing the Cluster‐Cloud and Its Role in Nanocrystallization

et al. 2019

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which emphasize the presences of several intermediate states prior to nucleation, such as amorphous precursors, [5c,6] magicsize clusters, [7] condensed liquid phase, [8] prenucleation clusters, [9] etc. Although it is suggested that the energetic barrier for multistep nucleation via intermediate states is lower than that expected in a classical nucleation picture, [10] debates remain due to the lack of direct experimental evidence for early crystallization. [4b,5a,c,7,11] The diversity and details of nonclassical nucleation and crystallization pathways (e.g., multistep nucleation process and amorphous precursor phase) of nanocrystals have been revealed at the nanoscale using liquid-cell transmission electron microscopy (LC-TEM). [5a,6b] The technical advancement of LC-TEM consists in its capability of tracking ultrasmall and metastable objects in solution, [5a,6b] making it a powerful tool to analyze liquid specimens and achieving in situ visualization with high spatial resolution. [12] Motivated by these recent advancements, we presently explore details in nanocrystallization [3] to achieve a full mechanistic understanding. In this communication, we analyze Pd and Au crystallizations using LC-TEM, and unravel an alternative nanocrystallization process involving an intermediate state which we dub clustercloud. This new phase plays a vital role in nucleation and particle structural evolution: the initial nucleation results from a sudden collapse of the cluster-cloud; and the subsequent particle maturation undergoes via the cluster-cloud mediated out-and-in relaxations. This discovery underscores the diversity and complexity of crystallization pathways and improves our current knowledge by providing a more comprehensive picture of nanocrystal formation.For the in situ LC-TEM observations of Pd and Au crystallization, solutions containing 400 nL 10.0 mm Na 2 PdCl 4 and HAuCl 4 , respectively, were prepared in the liquid-cells. Highenergy electrons from TEM generated solvated electrons to reduce solution Pd 2+[13] and Au 3+[14] to Pd and Au atoms, respectively (see Method in the Supporting Information for details). The time sequenced TEM images (Figure 1a) show the prenucleation and nucleation of Pd. Similar to Mirsaidov's observation of metal-rich liquid phase, [5a] a dark region formed (0 s), corresponding to the concentration of the reduced Pd atoms from solution. This irregular region was flexible with a cloud-like behavior (18 s). It is noteworthy that instead of a random assembly of atoms, this cloud consisted of several Elucidating the early stages of crystallization from supersaturated solutions is of critical importance, but remains a great challenge. An in situ liquid cell transmission electron microscopy study reveals an intermediate state of condensed atomic clusters during Pd and Au crystallizations, which is named a "cluster-cloud." It is found that nucleation is initiated by the collapse of a cluster-cloud, first forming a nanoparticle. The subsequent particle maturation proceeds via multi...

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Probing intermediates of the induction period prior to nucleation and growth of semiconductor quantum dots

Cited by 101 publications

References 80 publications

Two-Step Nucleation of CdS Magic-Size Nanocluster MSC–311

Two-Step Nucleation of CdS Magic-Size Nanocluster MSC–311

Revealing isoelectronic size conversion dynamics of metal nanoclusters by a noncrystallization approach

Revealing the Cluster‐Cloud and Its Role in Nanocrystallization

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