A population balance model of quantum dot formation: Oriented growth and ripening of ZnO

Segets, Doris; Hartig, Martin A.J.; Gradl, Johannes

doi:10.1016/j.ces.2011.04.043

Cited by 35 publications

(28 citation statements)

References 41 publications

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“…Particle formation of "simple" systems 21 can be modelled from a molecular perspective; modelling approaches of increasing complexity may even predict the dynamic evolution of particle size distributions and are the basis of any rigorous scale-up and process design. 22,23 However, the underlying reaction mechanisms and reaction pathways are largely unknown for most systems. Therefore, fundamental investigations of the forming phases and by-products are considered as first important steps towards the understanding of formation mechanisms from which knowledge-based guidelines may be derived on how to control nanoparticle formation.…”

Section: Introductionmentioning

confidence: 99%

A comprehensive study on the mechanism behind formation and depletion of Cu₂ZnSnS₄ (CZTS) phases

et al. 2015

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aHigh efficiency kesterite based solar cells have vigorously raised the research interests in this material. The challenge lies in understanding the formation and co-existence of more than 10 possible by-products during and after the synthesis of Cu 2 ZnSnS 4 (CZTS) and their various different structural and electronic defects.The present contribution shows an in-depth study on the stages of formation and depletion of nanoparticulate CZTS. Employing a hot injection synthesis method, we give direct experimental evidence of the co-existence of cubic, tetragonal and defected CZTS structures and different by-products as a function of time and temperature. SEM, (HR)TEM, XRD, EDX, ICP-OES, Raman spectroscopy and UV-Vis-NIR spectroscopy have been used in order to better evaluate and interpret data for crystal structures and compositions.The obtained understanding on the formation of different phases suggests 250°C as the most favourable synthesis temperature. Based on our study, general strategies can be developed for controlling the amount of formed phases, the by-products and the defects in kesterite and other similar multicomponent nanoparticles as well as in bulk systems.

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Section: Introductionmentioning

confidence: 99%

A comprehensive study on the mechanism behind formation and depletion of Cu₂ZnSnS₄ (CZTS) phases

et al. 2015

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“…However, this is rather ascribed to the low solubility of LiOH in the applied solvent ethanol leading to an incomplete dissolution of the hydroxide source [14,64]. With known reaction kinetics the ZnO concentration which is needed in the PBE to express the nucleation rate, is accessible…”

Section: Understanding Zno Nucleation and Growthmentioning

confidence: 99%

“…This was realized by population balance equations (PBE) which have been solved by using the commercially available program PARSIVAL by CiT GmbH [81]. For experimental details and specifications of the measurement devices the reader is again referred to the literature [14,64,65]. The most important findings will be summarized in the following.…”

Section: Analysis Of Reaction Controlled Particle Formationmentioning

confidence: 99%

“…D is the diffusion coefficient, c ZnO is the monomer concentration of ZnO molecules, N A is the Avogadro number, k B is the Boltzmann constant, T is the temperature, V M is the molecular volume of ZnO, γ is the surface tension that was determined experimentally [65], S is the supersaturation and ν is a stoichiometric factor [14,64].…”

Section: Understanding Zno Nucleation and Growthmentioning

confidence: 99%

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Process Engineering of Nanoparticles Below 20 nm—A Fundamental Discussion of Characterization, Particle Formation, Stability and Post Processing

Segets

2015

Colloid Process Engineering

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In the following chapter fundamental aspects that have to be considered during the processing of small nanoparticles will be addressed. We investigated quantum confined manganese doped ZnS, ZnO, PbS and PbSe semiconductor nanoparticles, so-called quantum dots (QDs) and silver noble metal nanorods. All materials were chosen due to their technical relevance for future applications in the emerging fields of solar cells, sensors and diagnostics as well as due to the possibility of their in situ characterization by UV/Vis absorbance spectroscopy. After a brief introduction to the specific prospects and challenges of these materials we will focus on the important processing issues that need to be solved for producing these particles at high quality on a larger scale: (i) the modelling of particle formation including nucleation, growth and ripening based on a mechanistic understanding and on experimentally derived data on solubility and surface energies, (ii) the stabilization of nanoparticles not only against agglomeration but also against shape changes and (iii) classification. The latter is realized by size selective precipitation which allows surprisingly sharp separations (κ = 0.75) of particles with only a few nm in diameter. Although the extremely small particle sizes (feed PSD between 1.5 and 3 nm), classification results were successfully analyzed by well-known concepts from particle technology. Our results are seen to be an essential contribution to colloidal processing. They enable a future optimization of process parameters by a knowledge-based design strategy that can be applied within continuous as well as automatized batch reactor concepts.

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“…Rather, the formation of dense, crystalline particles is implied. [1][2][3][4][5][6][7][8] For biominerals, such as CaCO 3 , amorphous intermediates have long been well known.…”

Section: Introductionmentioning

confidence: 99%

The evolution of crystalline ordering for ligand-ornamented zinc oxide nanoparticles

et al. 2016

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a Recent total scattering experiments have opened up the possibility to study nanoparticle formation in situ and to observe the structural transformation from precursor clusters to adult particles. Organic ligand molecules interact with precursors of metal oxide nanoparticles, yet their influence onto the evolution of crystallinity during particle formation has not been addressed in detail; nor have in situ total scattering experiments ventured into the field of low-concentration, room-temperature syntheses in organic solvents to date. In this report, we follow the crystallization of ZnO nanoparticles in ethanol in the presence of different organic ligands. Low coordinated zinc precursor clusters rapidly polymerize upon base addition to particles of ca. 1 nm in diameter. In situ SAXS experiments reveal that the overall particle size increases to 2 to 4 nm with advancing reaction time. Complementary in situ PDF experiments show smaller crystalline domain sizes, which are only one third to half as large as the particle diameter. The ZnO particles thus feature a crystalline core surrounded by a disordered shell. Both, the core and the shell diameter are influenced by the different surface-bound organic ligands, which prevent an immediate relaxation to fully crystalline particles. A slow crystallization takes place in solution. We assume a dynamic equilibrium of the ligand and solvent molecules at the particle surface, which enables gradual bond restructuring. With suitably adjusted synthesis conditions, in our case by a continuous base addition, we show how to bypass the disordered intermediates, allowing the spontaneous nucleation of fully crystalline nanoparticles.

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A population balance model of quantum dot formation: Oriented growth and ripening of ZnO

Cited by 35 publications

References 41 publications

A comprehensive study on the mechanism behind formation and depletion of Cu₂ZnSnS₄ (CZTS) phases

A comprehensive study on the mechanism behind formation and depletion of Cu₂ZnSnS₄ (CZTS) phases

Process Engineering of Nanoparticles Below 20 nm—A Fundamental Discussion of Characterization, Particle Formation, Stability and Post Processing

The evolution of crystalline ordering for ligand-ornamented zinc oxide nanoparticles

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A population balance model of quantum dot formation: Oriented growth and ripening of ZnO

Cited by 35 publications

References 41 publications

A comprehensive study on the mechanism behind formation and depletion of Cu2ZnSnS4 (CZTS) phases

A comprehensive study on the mechanism behind formation and depletion of Cu2ZnSnS4 (CZTS) phases

Process Engineering of Nanoparticles Below 20 nm—A Fundamental Discussion of Characterization, Particle Formation, Stability and Post Processing

The evolution of crystalline ordering for ligand-ornamented zinc oxide nanoparticles

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A comprehensive study on the mechanism behind formation and depletion of Cu₂ZnSnS₄ (CZTS) phases

A comprehensive study on the mechanism behind formation and depletion of Cu₂ZnSnS₄ (CZTS) phases