Mechanistic Study of the Role of Primary Amines in Precursor Conversions to Semiconductor Nanocrystals at Low Temperature

Yu, Kui; Li, Xiangyang; Chen, Queena Y.; Yang, Haoxiong; Yang, Mingli; Wang, Xinqin; Wang, Xin; Cao, Hu; Whitfield, Dennis M.; Hu, Changwei; Tao, Ye

doi:10.1002/ange.201403714

Cited by 8 publications

(16 citation statements)

References 47 publications

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“…Thus, the present study provides deeper insights into the induction period of colloidal semiconductor QD formation, which may share general developmental principles, such as those regarding the formation pathway of Cd 2 E 2 monomers and the existence of liquid-like clusters before and after nucleation and growth of RQDs. [42][43][44][45]55 The two-step nucleation mechanism proposed in the present study via intramolecular reorganization is promising and contributes to the fundamental base for future theoretical advances to resolve the mysteries and to reveal the beauty of crystal nucleation. We are actively studying additional experiments to further elucidate that the nucleation of MSC−311 is concentration-independent ( Figure 2) and is thus supersaturation-independent.…”

Section: ■ Conclusionmentioning

confidence: 70%

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: ■ Conclusionmentioning

confidence: 70%

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

et al. 2017

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“…The addition of amine ( Fig. 4b ) leads to the product 2c (Ph 2 P(Se)–NHC 18 H 35 ), in addition to 1d and salt Ph 2 P(Se 2 )NH 2 C 18 H 35 (which can have resulted from the reaction of Se=PPh 2 H+C 18 H 35 NH 2 ) 16 24 25 . The addition of alcohol ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…4f with both the presence of Cu and In). Thus, the observation of Compounds 1 and 2 could be affected by several factors, including the equilibrium of 1 +Se=PPh 2 H⇌ 2 +HPPh 2 , which could be weighted towards the right ( Supplementary Table 2 and Supplementary Note 2 ), similar to TOP+Se=PPh 2 H⇌SeTOP+HPPh 2 (refs 15 , 23 ), except for 1b +Se=PPh 2 H⇌ 2b +HPPh 2 (refs 21 , 23 , 24 , 25 ).…”

Section: Resultsmentioning

confidence: 99%

“…With the monomer in the form of Cd 1 Se 1 instead of Cd 2 Se 2 , the pathway from precursors to Cd 1 Se 1 monomers was recently documented for CdSe NCs in the presence of C 18 H 35 NH 2 as one additive from the reaction of Cd(OA) 2 +SeTOP+HPPh 2 . The P-containing products Ph 2 P-OOCC 17 H 33 ( 1a ), Ph 2 P−PPh 2 ( 1b ), Ph 2 P-NHC 18 H 35 ( 1c ) and Ph 2 P(Se)–NHC 18 H 35 ( 2c ) were detected, and the equilibrium of 1c +Se=PPh 2 H⇌ 2c +HPPh 2 was demonstrated 25 . Different NC systems are supposed to follow different reaction pathways to their monomers; for this seemingly obvious reason, we decided to investigate individual pathways from precursor evolution to monomers at low reaction temperatures in each of the reactions of MX n + nE =PPh 2 H+H Y , where M =Cu (I), Cd (II), Zn (II), Ge (II), Pb (II) and In (III), E =S, Se and Te, and H Y = R COOH, HPPh 2 , R NH 2 , R SH and R OH.…”

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confidence: 99%

“…Colloidal semiconductor nanocrystal (NC) quantum dots (QDs) with distinct properties and well-acknowledged potential in many applications such as light-emitting diodes 1 2 , lasing 3 4 , photovoltaics 5 6 and bio-labelling/imaging 7 8 9 have been the focus of intense research ranging from fundamental science to applied technologies. For the past two decades, there have been significant efforts made to advance NC syntheses 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 . Mainly, the wet-chemical synthesis of colloidal metal chalcogenide NCs depends on the use of metal salts such as cadmium oleate (Cd(OA) 2 or Cd(OOCC 17 H 33 ) 2 ) and tri- n -octylphosphine chalcogenides ( E =P(C 8 H 17 ) 3 or E TOP, E =S, Se, and Te), together with beneficial additives in 1-octadecene (ODE) including diphenylphosphines 13 14 15 16 17 18 19 , primary alkyl amines 16 25 26 27 28 29 30 35 36 , thiols 22 29 30 31 and alcohols 14 27 34 .…”

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General low-temperature reaction pathway from precursors to monomers before nucleation of compound semiconductor nanocrystals

et al. 2016

Nat Commun

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Little is known about the molecular pathway to monomers of semiconductor nanocrystals. Here we report a general reaction pathway, which is based on hydrogen-mediated ligand loss for the precursor conversion to ‘monomers' at low temperature before nucleation. We apply 31P nuclear magnetic resonance spectroscopy to monitor the key phosphorous-containing products that evolve from MXn+E=PPh2H+HY mixtures, where MXn, E=PPh2H, and HY are metal precursors, chalcogenide precursors, and additives, respectively. Surprisingly, the phosphorous-containing products detected can be categorized into two groups, Ph2P–Y and Ph2P(E)–Y. On the basis of our experimental and theoretical results, we propose two competing pathways to the formation of M2En monomers, each of which is accompanied by one of the two products. Our study unravels the pathway of precursor evolution into M2En monomers, the stoichiometry of which directly correlates with the atomic composition of the final compound nanocrystals.

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Fragmentation of Magic‐Size Cluster Precursor Compounds into Ultrasmall CdS Quantum Dots with Enhanced Particle Yield at Low Temperatures

Zhang

et al. 2020

Angewandte Chemie

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Colloidal small‐size CdS quantum dots (QDs) are produced usually with low particle yield, together with side products such as the particular precursor compounds (PCs) of magic‐size clusters (MSC). Here, we report our synthesis of small‐size CdS QDs without the coexistence of the PC and thus with enhanced particle yield. For a conventional reaction of cadmium oleate (Cd(OA)2) and sulfur (S) in 1‐octadecene (ODE), we show that after the formation of the PC in the pre‐nucleation stage, the addition of tri‐n‐octylphosphine oxide (TOPO) facilitates the production of small‐size QDs. We demonstrate that TOPO fragmentizes the PC that have formed, which enables the nucleation and growth of small‐size QDs even at room temperature. Our findings introduce a new approach to making small‐size QDs without the coexistence of the PC and with improved particle yield. Providing experimental evidence for the two‐pathway model proposed for the pre‐nucleation stage of colloidal binary QDs, the present study aids in the advance of non‐classical nucleation theory.

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Mechanistic Study of the Role of Primary Amines in Precursor Conversions to Semiconductor Nanocrystals at Low Temperature

Cited by 8 publications

References 47 publications

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

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

General low-temperature reaction pathway from precursors to monomers before nucleation of compound semiconductor nanocrystals

Fragmentation of Magic‐Size Cluster Precursor Compounds into Ultrasmall CdS Quantum Dots with Enhanced Particle Yield at Low Temperatures

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