Center for Molecular Modeling - Z. Hens

Mechanistic Insights in Seeded Growth Synthesis of Colloidal Core/Shell Quantum Dots

msluydts — Fri, 19 May 2017 19:01:55 +0000

I. Nakonechnyi, M. Sluydts, Y. Justo, J. Jasieniak, Z. Hens

Chemistry of Materials

29 (11), 4719-4727

2017

Abstract

We analyze the mechanism of seeded growth reactions used to synthesize colloidal core/shell nanocrystals. Looking at the formation of CdSe/CdS and CdSe/ZnSe using both zinc blende and wurtzite CdSe seeds with a different surface termination, we show that the formation rate of the shell material does not depend on the presence of the CdSe seed nanocrystals. This suggests that shells grow by inclusion of CdS or ZnSe initially formed in the reaction mixture, possibly under the form of reactive monomers, and not by successive adsorption and reaction of metal and chalcogen precursors. This insight makes balancing homogeneous nucleation and heterogeneous growth of the shell material key to suppressing spurious secondary nucleation. Through a combination of experimental work and reaction simulations, we show that this can be effectively achieved by raising the monomer solubility through the concentration of carboxylic acid used in the seeded growth reaction.

DOI

http://dx.doi.org/10.1021/acs.chemmater.7b00354

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acs.chemmater.7b00354.pdf

Ligand Addition Energies and the Stoichiometry of Colloidal Nanocrystals

msluydts — Wed, 30 Dec 2015 08:55:46 +0000

M. Sluydts, K. De Nolf, V. Van Speybroeck, S. Cottenier, Z. Hens

ACS Nano

10 (1), 1462-1474

2016

Abstract

Experimental non-stoichiometries of colloidal nanocrystals such as CdSe and PbS are accounted for by attributing to each constituent atom and capping ligand a formal charge equal to its most common oxidation state to obtain an overall neutral nanocrystal. In spite of its apparent simplicity, little theoretical support of this approach - called here the oxidation-number sum rule - is present in the current literature. Here, we introduce the ligand addition energy, which we define as the energy gained or expended upon the transfer of one ligand from a reference state to a (metal-rich) solid surface. For the combination of CdSe, ZnSe and InP with either chalcogen, halogen or hydrochalcogen ligands, we compute successive ligand addition energies using ab initio methods and determine the thermodynamically stable surface composition as that composition where ligand addition turns endothermic. We find that the oxidation-number sum rule is valid in many situations, although exceptions occur for each material studied most notably when exposed to small oxidative ligands. In the case of InP violations are more severe, extending towards the entire chalcogen ligand family. In addition, we find that electronegativity rather than chemical hardness is a reasonable predictor for ligand addition energies, with the most electronegative ligands yielding the most exothermic addition energies. Finally, we argue that the ligand addition energy will be a most useful quantity for future computational studies on the structure, stability and reactivity of nanocrystal surfaces.

DOI

http://dx.doi.org/10.1021/acsnano.5b06965

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16-ACSNano-10(1)1462-Sluydts.pdf

Controlling the Size of Hot Injection Made Nanocrystals by Manipulating the Diffusion Coefficient of the Solute

wim — Tue, 28 Apr 2015 07:35:02 +0000

K. De Nolf, R.K. Capek, S. Abé, M. Sluydts, Y. Jang, J.C. Martins, S. Cottenier, E. Lifshitz, Z. Hens

JACS (Journal of the American Chemical Society)

137 (7), 2495–2505

2015

Abstract

We investigate the relation between the chain length of ligands used and the size of the nanocrystals formed in the hot injection synthesis. With two different CdSe nanocrystal syntheses, we consistently find that longer chain carboxylic acids result in smaller nanocrystals with improved size dispersions. By combining a more in-depth experimental investigation with kinetic reaction simulations, we come to the conclusion that this size tuning is due to a change in the diffusion coefficient and the solubility of the solute. The relation between size tuning by the ligand chain length and the coordination of the solute by the ligands is further explored by expanding the study to amines and phosphine oxides. In line with the weak coordination of CdSe nanocrystals by amines, no influence of the chain length on the nanocrystals is found, whereas the size tuning brought about by phosphine oxides can be attributed to a solubility change. We conclude that the ligand chain length provides a practical handle to optimize the outcome of a hot injection synthesis in terms of size and size dispersion and can be used to probe the interaction between ligands and the actual solute.

DOI

http://dx.doi.org/10.1021/ja509941g

Private attachment

15_JACS_137(7)2495_DeNolf.pdf

Ligand Addition Energy and the Stoichiometry of Colloidal Nanocrystals

samuel — Thu, 06 Feb 2020 09:12:02 +0000

K. De Nolf, M. Sluydts, V. Van Speybroeck, S. Cottenier, Z. Hens

ISBN/ISSN:

Talk

Conference / event / venue

2019 MRS (Materials Research Society) Spring Meeting & Exhibit

Phoenix, AZ, USA

Monday, 28 March, 2016 to Saturday, 2 April, 2016

Ligand Addition Energies and the Stoichiometry of Colloidal Nanocrystals

msluydts — Wed, 08 Jun 2016 11:56:58 +0000

M. Sluydts, K. De Nolf, V. Van Speybroeck, S. Cottenier, Z. Hens

ISBN/ISSN:

Talk

Conference / event / venue

EMRS Spring Meeting 2016

Lille, France

Monday, 2 May, 2016 to Friday, 6 May, 2016

Abstract

emrsabstract1.txt

Conference reference

EMRS Spring Meeting 2016

Hard of soft? Validation of HSAB theory for inorganic ligand adsorption on colloidal nanocrystals

msluydts — Wed, 01 Jul 2015 13:53:16 +0000

M. Sluydts, Z. Hens, V. Van Speybroeck, S. Cottenier

ISBN/ISSN:

Poster

Conference / event / venue

Euro-TMCS I

Granada, Spain

Wednesday, 28 January, 2015 to Friday, 30 January, 2015

Ligand engineering of colloidal nanocrystals

msluydts — Wed, 15 Jan 2014 08:02:13 +0000

M. Sluydts, Z. Hens, V. Van Speybroeck, S. Cottenier

ISBN/ISSN:

Talk

Conference / event / venue

14th UGent FEA PhD Symposium

Ghent Belgium

Friday, 6 December, 2013

Abstract (private)

phdsymposium2013.pdf

Ligand engineering of colloidal nanocrystals

msluydts — Wed, 15 Jan 2014 08:01:56 +0000

M. Sluydts, Z. Hens, V. Van Speybroeck, S. Cottenier

ISBN/ISSN:

Poster

Conference / event / venue

14th UGent FEA PhD Symposium

Ghent Belgium

Friday, 6 December, 2013

Abstract (private)

phdsymposium2013.pdf

Ab initio modeling of ligand adsorption on colloidal CuInS2 quantum dots

msluydts — Tue, 14 Jan 2014 11:02:48 +0000

M. Sluydts, Z. Hens, V. Van Speybroeck, S. Cottenier

N-10

ISBN/ISSN:

Poster

Conference / event / venue

EMRS Spring Meeting 2013

Strasbourg France

Monday, 27 May, 2013 to Friday, 31 May, 2013

Abstract (private)

Ab initio modeling of ligand adsorption on colloidal CuInS2 quantum dots.pdf

Conference reference

EMRS Spring Meeting 2013

FWO NANO (3G076012)

wim — Tue, 23 Apr 2013 13:43:25 +0000

Project promotor

Z. Hens, V. Van Speybroeck, S. Cottenier

Financierende instantie

FWO

Project data

01/01/2012 to 31/12/2015

Bedrag

€300 000,00

Project titel

I-III-VI2 Halfgeleider Nanokristallen, van een fundamenteel begrip van de hot injection synthese tot een nieuwe materiaalfamilie van colloïdale kwantum dots.

Personeel

M. Sluydts

Project ref.

FWO NANO (3G076012) B/12578/*