Contribution of Ex-Situ and In-Situ X-ray Grazing Incidence Scattering Techniques to the Understanding of Quantum Dot Self-Assembly: A Review

Saxena, Vishesh; Portale, Giuseppe

doi:10.3390/nano10112240

Cited by 9 publications

(9 citation statements)

References 68 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The origin of a certain superlattice configuration for the case of PbS NCs is still a subject of ongoing research because, even at seemingly similar conditions, different self-assembled superlattice structures have been observed. , The recently emerged in situ X-ray scattering methods of the self-assembly characterization represent a promising route for providing insights into the assembly mechanism and uncover the time-resolved superlattice transitions. − However, the discussion and determination of the ligand grafting density are often absent in the literature, which complicates comparison between experimental results obtained for similar systems in independent investigations and hinder the development of theoretical models that would help to navigate the assembly pathway to produce the targeted superlattices.…”

Section: Introductionmentioning

confidence: 99%

Real-Time X-ray Scattering Discovers Rich Phase Behavior in PbS Nanocrystal Superlattices during In Situ Assembly

et al. 2021

View full text Add to dashboard Cite

During the self-organization of colloidal semiconductor nanoparticles by solvent evaporation, nanoparticle interactions are substantially determined by the organic ligands covering the inorganic core. However, the influence of the ligand grafting density on the assembly pathway is often not considered in experiments. Here, we carry out an in situ synchrotron small-angle X-ray scattering and X-ray cross-correlation analysis study of the real-time assembly of oleic acid-capped PbS nanocrystals at a low ligand coverage of 2.7 molecules/nm2. With high temporal and spatial resolution, we monitor the transitions from the colloidal suspension through the solvated superlattice states into the final dried superstructure. In a single in situ experiment, we observe a two-dimensional hexagonal, hexagonal close-packed, body-centered cubic, body-centered tetragonal (with different degrees of tetragonal distortion), and face-centered cubic superlattice phases. Our results are compared to the self-organization of PbS nanocrystals with a higher ligand coverage up to 4.5 molecules/nm2, revealing different assembly pathways. This highlights the importance of determining the ligand coverage in assembly experiments to approach a complete understanding of the assembly mechanism as well as to be able to predict and produce the targeted superstructures.

show abstract

Section: Introductionmentioning

confidence: 99%

Real-Time X-ray Scattering Discovers Rich Phase Behavior in PbS Nanocrystal Superlattices during In Situ Assembly

et al. 2021

View full text Add to dashboard Cite

show abstract

“…X-ray diffraction (XRD) is one of the most widespread approaches to the characterization of nanomaterials. − Specifically, small- and wide-angle X-ray scattering (especially grazing-incidence techniques) − are used to study the structure of colloidal nanocrystal superlattices and assemblies. Experiments with these techniques are performed with dedicated benchtop instruments or at specific synchrotron beamlines, and hence they are bound to instrumental accessibility.…”

mentioning

confidence: 99%

Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals

et al. 2021

View full text Add to dashboard Cite

Colloidal superlattices are fascinating materials made of ordered nanocrystals, yet they are rarely called “atomically precise”. That is unsurprising, given how challenging it is to quantify the degree of structural order in these materials. However, once that order crosses a certain threshold, the constructive interference of X-rays diffracted by the nanocrystals dominates the diffraction pattern, offering a wealth of structural information. By treating nanocrystals as scattering sources forming a self-probing interferometer, we developed a multilayer diffraction method that enabled the accurate determination of the nanocrystal size, interparticle spacing, and their fluctuations for samples of self-assembled CsPbBr3 and PbS nanomaterials. The multilayer diffraction method requires only a laboratory-grade diffractometer and an open-source fitting algorithm for data analysis. The average nanocrystal displacement of 0.33 to 1.43 Å in the studied superlattices provides a figure of merit for their structural perfection and approaches the atomic displacement parameters found in traditional crystals.

show abstract

“…In this way, the penetration depth of X‐rays can be tuned, typically from below 1 nm up to several 100 nm and thus the surface‐sensitivity can be adjusted. [ 233,234 ]…”

Section: X‐ray Scattering Methodsmentioning

confidence: 99%

“…Here, GISAXS is the method of choice, providing structural information at and close to the interface with high spatial resolution normal to the interface. A recent review focuses particularly on quantum dot self‐assembly probed by GISAXS, [ 234 ] so the discussion here is restricted to some recent highlights.…”

Section: X‐ray Scattering Methodsmentioning

confidence: 99%

“…In this way, the penetration depth of X-rays can be tuned, typically from below 1 nm up to several 100 nm and thus the surfacesensitivity can be adjusted. [233,234] The GISAXS geometry is shown in Figure 5. Similar to SAXS experiments, the scattered intensity is measured on a 2D detector several meters downstream the sample.…”

Section: Grazing-incidence Small-angle X-ray Scattering (Gisaxs)mentioning

confidence: 99%

See 1 more Smart Citation

Recent Notable Approaches to Study Self‐Assembly of Nanoparticles with X‐Ray Scattering and Electron Microscopy

Schulz

Lokteva

Parak

et al. 2021

Part & Part Syst Charact

View full text Add to dashboard Cite

several issues far from being resolved: for many systems long-range periodic order is not routinely achieved, reproducibility is often not optimal and truly emergent and new properties arising from the supercrystal formation could be demonstrated for just a few systems. [3][4][5][6][7] From the materials science perspective there is no established figure of merit or common set of parameters allowing to quantify "quality" of NP superlattices and supercrystals. In lieu of such standard procedures, terms as well-ordered, crystalline order, quasicrystalline, etc., are usually used in literature. However, there exist no commonly accepted definitions of what qualifies, e.g., as "well-ordered."In this review, we want to highlight some recent experimental developments and new approaches to study self-assembly of NPs or structure formation of NP supercrystals and their final structure. We focus on NP, the broad field of photonic materials prepared by self-assembly of larger colloidal particles is not covered herein. [8][9][10] The introduction of the basic concepts of NP self-assembly will be kept short and should be considered as an overview, for more background and details excellent comprehensive reviews are available. [2,11] We will then briefly address and discuss the expectations associated with self-assembled materials, especially the proposed emergence of new properties directly related to order. In the second part of the review, we will present recent innovative approaches for the investigation of self-assembly and self-assembled structures that go beyond the standard characterization. We focus mainly on structure and structure formation and less on properties, so most of the studies are based on scattering and electron microscopy. Figure 1 provides an overview roughly following this outline. Self-Assembly of NanoparticlesSelf-assembly is a broad term and occurs on all scales from atoms, ions, and molecules to galaxies, as pointed out by Whitesides and Grzybowski. [12] It can be defined as the autonomous organization of multiple discrete components into ordered structures, driven by energetics or entropy or both. [2,13] In nature, countless examples of highly complex and functional structures resulting from self-assembly can be found, Self-assembly of nanoparticles (NPs) has evolved into a powerful tool for the synthesis of superstructures with tailored properties. The quality, diversity, and complexity of synthesized structures are continuously improving and fascinating new collective properties are demonstrated. At the same time, the rapid development of electron microscopy and synchrotron sources for X-rays has enabled new exciting experimental approaches to study structure and structure formation in the context of NP self-assembly. In this review, some recent studies and what can be learned from them are highlighted and discussed. It is started with a general introduction covering important concepts, experimental approaches, commonly obtained structures, the ideas of artificial atoms, and emerging properties a...

show abstract

Contribution of Ex-Situ and In-Situ X-ray Grazing Incidence Scattering Techniques to the Understanding of Quantum Dot Self-Assembly: A Review

Cited by 9 publications

References 68 publications

Real-Time X-ray Scattering Discovers Rich Phase Behavior in PbS Nanocrystal Superlattices during In Situ Assembly

Real-Time X-ray Scattering Discovers Rich Phase Behavior in PbS Nanocrystal Superlattices during In Situ Assembly

Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals

Recent Notable Approaches to Study Self‐Assembly of Nanoparticles with X‐Ray Scattering and Electron Microscopy

Contact Info

Product

Resources

About