<i>In situ</i> extended x-ray absorption fine structure study of initial processes in CdSe nanocrystals formation using a microreactor

Uehara, Masato; Sun, Zhihu; Ōyanagi, H.; Yamashita, Kenichi; Fukano, Atsuyuki; Nakamura, Hiroyuki; Maeda, Hideaki

doi:10.1063/1.3080660

Cited by 26 publications

(37 citation statements)

References 23 publications

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“…A different but also important study [45] also demonstrated the nucleation and the growth mechanism of the CdSe NPs using in situ fluorescence detected extended X-ray absorption spectroscopy (EXAFS) [46] and ex situ UV-Vis absorption techniques. The data collected via these two techniques were taken under the same conditions.…”

Section: In Situ Characterization Techniquesmentioning

confidence: 99%

Theories of nanoparticle and nanostructure formation in liquid phase

Karatutlu

Barhoum

Sapelkin

2018

Emerging Applications of Nanoparticles and Architecture Nanostructures

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598 CHAPTER 20 Theories of nanoparticle and nanostructure formation in liquid phase and crystallization. In general, tiny NP "clusters" are gathered together to form NPs, and then the NPs are assembled to form nanostructures. In bottom-up approaches, cluster formation and nucleation are the first steps in NP formation, and they are the most crucial steps in controlling the crystal structure, size, shape, and surface characteristics of NPs [9]. Nucleation is the process whereby nuclei (seeds) act as templates for crystal growth. Nucleation may happen in the solution homogeneously or heterogeneously. Homogeneous nucleation occurs when nuclei form uniformly within the parent phase, whereas heterogeneous nucleation forms on a solid support (nucleating surface), such as container surfaces, impurities, grain boundaries, or dislocations [10]. In general, heterogeneous nucleation occurs much more easily than homogenous nucleation, since a stable nucleating surface is already present.The fundamental phenomena involved in crystallization from solutions via nucleation and growth is still a hot topic [11]. Recently, significant efforts have been directed to understanding the mechanism of NP formation in solutions [12][13][14]. In particular, attention has been directed to study the wide varieties of additives and their influences on prenucleation clusters, nucleation, crystallization, nanocrystal assembly, and thus morphologies.The importance of NPs and nanostructures in many fields of science and technology has spurred a high level of research activity and led to the formulation of well-established theories for nucleation and crystal growth. This chapter highlights the different theories, such as classical nucleation theory (CNT), La Mer's nucleation and growth mechanisms, the two-step nucleation and growth mechanism, and the prenucleation cluster (PNC) mechanism. Subsequently in situ experimental characterization for NP formation, including nucleation and growth processes, will be highlighted, and what occurs within the different processes outlined. ■ ■ FIGURE 20.9 (A) The processes of Au depositing on a Pt icosahedral nanocrystal is schematically demonstrated. (B) The nucleation and growth of Au on Pt nanocrystals are quantitatively analyzed. (Source: Reproduced with permission from Ref. [47]. 615 6 In situ characterization techniques ■ ■ FIGURE 20.10 Radius, concentration, and size distribution from the SAXS fitting results. (A) The results of the fit of the SAXS patterns are presented as a function of time. For the two different ligands, the concentration of particles (n/N A ), the center of the Gaussian distribution, and the σ parameter are designated. (B) SAXS patterns for the first instants of the reaction and the corresponding fits for an acid ligand are shown. (C) Corresponding size distribution is given for the SAXS patterns presented in (B). (Source: Reproduced with permission from Ref. [48].

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Section: In Situ Characterization Techniquesmentioning

confidence: 99%

Theories of nanoparticle and nanostructure formation in liquid phase

Karatutlu

Barhoum

Sapelkin

2018

Emerging Applications of Nanoparticles and Architecture Nanostructures

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“…The synthesis of the CdSe QDs was modified from the original organometallic procedure [18] for utilization of the microfluidic reactor [9,17,19]. Three raw material stock solutions (Se source, Cd source and ligand solutions) were prepared under a dry nitrogen atmosphere.…”

Section: Methodsmentioning

confidence: 99%

In-situ EXAFS study of nucleation process of CdSe nanocrystals

Sun¹,

Ōyanagi²,

Uehara³

et al. 2009

J. Phys.: Conf. Ser.

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“…There are two peaks at approximately 1.7Å and 2.3Å without a phase shift. Based on previous results [21,31,[39][40][41], the Cd-Se bond has a peak between 2.0 and 3.2Å in the Cd K-edge RSF function. In our results, there is a peak at approximately 2.3Å without a phase shift, which was confirmed to be from the Cd-Se bond.…”

Section: Journal Of Nanomaterialsmentioning

confidence: 64%

The Core/Shell Structure of CdSe/ZnS Quantum Dots Characterized by X‐Ray Absorption Fine Spectroscopy

Wei

Zhou

Zhang

et al. 2015

Journal of Nanomaterials

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Understanding the chemical and physical properties of core/shell nanocrystal quantum dots (QDs) is key for their use in light-emission applications. In this paper, a single-step injection-free scalable synthetic method is applied to prepare high-quality core/shell QDs with emission wavelengths of 544 nm, 601 nm, and 634 nm. X-ray absorption fine structure spectra are used to determine the core/shell structure of CdSe/ZnS quantum dots. Moreover, theoretical XANES spectra calculated by FEFF.8.20 are used to determine the structure of Se and S compounds. The QD samples displayed nearly spherical shapes with diameters of approximately 3.4 ± 0.5 nm (634 nm), 4.5 ± 0.4 nm (601 nm), and 5.5 ± 0.5 nm (544 nm). With XANES results and MS calculations, it is indicated that sphalerite ZnS capped with organic sulfur ligands should be the shell structure. Wurtzite CdSe is the main core structure with a Cd-Se bond length of 2.3 Å without phase shift. This means that different emission wavelengths are only due to the crystal size with single-step injection-free synthesis. Therefore, single-step injection-free synthesis could generate a nearly ideal core/shell structure of CdSe/ZnS QDs capped with an organic sulfur ligand.

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In situ extended x-ray absorption fine structure study of initial processes in CdSe nanocrystals formation using a microreactor

Cited by 26 publications

References 23 publications

Theories of nanoparticle and nanostructure formation in liquid phase

Theories of nanoparticle and nanostructure formation in liquid phase

In-situ EXAFS study of nucleation process of CdSe nanocrystals

The Core/Shell Structure of CdSe/ZnS Quantum Dots Characterized by X‐Ray Absorption Fine Spectroscopy

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