Heterogeneous local order in self-assembled nanoparticle films revealed by X-ray cross-correlations

Lehmkühler, Felix; Schulz, Florian; Schroer, Martin A.; Frenzel, Lara; Lange, Holger; Grübel, G.

doi:10.1107/s2052252518005407

Cited by 15 publications

(30 citation statements)

References 51 publications

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“…1(b) (de Jeu, 2016). Such aggregates may originate from the formation of cracks during drying and are in addition visible by scanning electron microscopy as shown previously (Lehmkü hler et al, 2018).…”

Section: Resultssupporting

confidence: 61%

“…Under these conditions the solutions dry in a well defined volume and the film thickness can be controlled by the AuNP concentration. This way, film thicknesses between approximately 100 and 600 nm are obtained (Lehmkü hler et al, 2018). For each film, 7.5 ml solutions of AuNP with the different ligands and salt content described above were pipetted onto the framed membrane and dried at 338 K.…”

Section: Sample Preparationmentioning

confidence: 99%

“…Recently, the potential of XCCA has been demonstrated by various theoretical and simulation studies on 2D systems (Altarelli et al, 2010;Kurta et al, 2012;Lehmkü hler et al, 2014;Malmerberg et al, 2015;Latychevskaia et al, 2015;Martin, 2017;Lhermitte et al, 2017) and shown experimentally for thin polymer systems and NPs (Gutt et al, 2014;Schroer et al, 2015;Liu et al, 2017;, liquid crystals (Zaluzhnyy, Kurta, Sulyanova et al, 2017), and colloids and nanocrystals (Mendez et al, 2014;Mancini et al, 2016;Schroer, Westermeier et al, 2016;Mendez et al, 2016;Zaluzhnyy, Kurta, André et al, 2017;Mancini et al, 2018). We previously measured the local orientational order of self-assembled NP films of thicknesses of up to a few micrometres by means of XCCA (Schroer et al, 2015;Lehmkü hler et al, 2018).…”

Section: Introductionmentioning

confidence: 98%

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Local orientational order in self-assembled nanoparticle films: the role of ligand composition and salt

Lehmkühler¹,

Schulz²,

Schroer³

et al. 2019

J Appl Cryst

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An X-ray cross-correlation study of the local orientational order in selfassembled films made from PEGylated gold nanoparticles is presented. The local structure of this model system is dominated by four-and sixfold order. Coadsorption of shorter ligands in the particle's ligand layer and variation of salt concentration in the suspension prior to self-assembly result in a change of local orientational order. The degree of sixfold order is reduced after salt addition. This decrease of order is less pronounced for the fourfold symmetry. The results presented here suggest complex symmetry-selective order formation upon ligand exchange and salt addition and demonstrate the versatility of X-ray crosscorrelation methods for nanoparticle superlattices. research papers J. Appl. Cryst. (2019). 52, 777-782 Felix Lehmkü hler et al. Local orientational order in self-assembled nanoparticle films 781

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Section: Resultssupporting

confidence: 61%

Section: Sample Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Local orientational order in self-assembled nanoparticle films: the role of ligand composition and salt

Lehmkühler¹,

Schulz²,

Schroer³

et al. 2019

J Appl Cryst

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“…Due to small variations in the sample volume and the solvent amount needed for chamber saturation, the absolute time differs from that shown in Figure a. Cross‐correlations of Bragg reflections have been recently demonstrated as a valuable tool to access structural information beyond conventional pair‐correlation as probed in the standard SAXS analysis. Here, Fourier coefficients of the correlation function

C (q, Δ) = \frac{〈 I (q, ϕ) I {(q, ϕ + Δ 〉}_{ϕ} - {〈 I (q, ϕ) 〉}_{ϕ}^{2}}{{〈 I (q, ϕ) 〉}_{ϕ}^{2}}

are calculated from the 2D diffraction patterns.…”

Section: Resultsmentioning

confidence: 99%

Monitoring Nanocrystal Self‐Assembly in Real Time Using In Situ Small‐Angle X‐Ray Scattering

Lokteva

Koof

Walther

et al. 2019

Small

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involve a variety of interactions and driving forces between inorganic hard core, organic soft surface-coating ligands, and surrounding solvent molecules. [2,[7][8][9] As a consequence, a thorough understanding of a solvent-mediated assembly process is required to produce NC solids with programmable properties.Here, we have chosen lead sulfide (PbS) nanocrystals as a model system for the investigation of the in situ self-assembly due to the possibility to produce monodisperse particles in a colloidal solution with a precisely controlled size. Additionally, the unique electronic properties of semiconductor PbS NCs with tunable bandgap make them attractive for many potential technological applications, including solar cells, light-emitting diodes, transistors, photodetectors, etc. [10][11][12][13] The structure and degree of order in NC superlattices depend on several factors, such as NC size and shape, ligand length, grafting density, ligand-solvent interactions, NC concentration, solvent evaporation rate (in case of evaporative assembly), and cell geometry or substrate where the assembly takes place. Thus, recent studies on lead chalcogenide NC assemblies revealed the formation of face-centered cubic (fcc) or body-centered cubic (bcc) superstructures as well as lattice distorted facecentered tetragonal (fct) and body-centered tetragonal (bct) superlattices. [14][15][16][17][18] However, their assembling mechanism remains largely unresolved mainly due to the challenge in measuring intermediate transitions between the initial colloidal state and the final superlattice state, especially in real time.Recently, in situ scattering methods have emerged as a powerful characterization tool to study the nucleation and growth of nanoparticle superlattices. [19][20][21][22] Small-angle X-ray scattering (SAXS) allows for monitoring the self-assembly dynamics with subsecond temporal resolution over large sample volumes under controlled conditions (e.g., controlled solvent vapor environment and temperature) and provides realtime information on long range order in the assembled structures. Often, the grazing-incidence small-angle X-ray scattering (GISAXS) technique is applied for in situ measurements, where a drop of nanocrystal suspension is placed on a substrate and evaporated in a controlled manner. [16,20,23,24] However, at small incident angles of the X-ray beam GISAXS is able to probe only up to several monolayers and is thus limited to the surface regime. For bulk measurements transmission SAXS is Self-assembled nanocrystal superlattices have attracted large scientific attention due to their potential technological applications. However, the nucleation and growth mechanisms of superlattice assemblies remain largely unresolved due to experimental difficulties to monitor intermediate states. Here, the self-assembly of colloidal PbS nanocrystals is studied in real time by a combination of controlled solvent evaporation from the bulk solution and in situ small-angle X-ray scattering (SAXS) in transmission geometry. For the fi...

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“…[28][29][30] Upon evaporation of the solvent, AuNP@PEG can form extended solids with locally ordered domains. 31 The addition of salt decreases the solubility of PEG in water and at high salt concentrations, aggregation of the free polymer can occur depending on the type of salt. [32][33][34] Zámbó et al demonstrated that the lower critical solution temperature of AuNP@PEG can be lowered effectively by the addition of K 2 SO 4.…”

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confidence: 99%

Pressure-Stimulated Supercrystal Formation in Nanoparticle Suspensions

Schroer

Lehmkühler

Möller

et al. 2018

J. Phys. Chem. Lett.

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Nanoparticles can self-organize into "supercrystals" with many potential applications. Different paths can lead to nanoparticle self-organization into such periodic arrangements. An essential step is the transition from an amorphous state to the crystalline one. We investigate how pressure can induce a phase transition of a nanoparticle model system in water from the disordered liquid state to highly ordered supercrystals. We observe reversible pressure-induced supercrystal formation in concentrated solutions of gold nanoparticles by means of small-angle X-ray scattering. The supercrystal formation occurs only at high salt concentrations in the aqueous solution. The pressure dependence of the structural parameters of the resulting crystal lattices is determined. The observed transition can be reasoned with the combined effect of salt and pressure on the solubility of the organic PEG shell that passivates the nanoparticles.

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Heterogeneous local order in self-assembled nanoparticle films revealed by X-ray cross-correlations

Abstract: An X-ray cross-correlation study of the self-assembly of soft-shell nanoparticles is presented. It is demonstrated that the assembled films are structurally heterogeneous, with dominant hexagonal and cubic symmetries forming patches of 104–105 particles.

Cited by 15 publications

References 51 publications

Local orientational order in self-assembled nanoparticle films: the role of ligand composition and salt

Local orientational order in self-assembled nanoparticle films: the role of ligand composition and salt

Monitoring Nanocrystal Self‐Assembly in Real Time Using In Situ Small‐Angle X‐Ray Scattering

Pressure-Stimulated Supercrystal Formation in Nanoparticle Suspensions

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