Structure–Transport Correlation Reveals Anisotropic Charge Transport in Coupled PbS Nanocrystal Superlattices

Zhang

et al. 2021

Small

Mixed‐dimensional heterostructures (MDHs), which combine nanomaterials of different dimensionalities deliver on the promise to bypass intrinsic limitations of a given low‐dimensional material. Here, a strategy to engineer MDHs between two low‐dimensional materials by curvature‐complementary self‐assembly is described. CdSe nanotubes rolled from 2D nanosheets and 1D CdSe nanorods, with negative and positive curvatures, respectively, are selected to illustrate complementary curvature self‐assembly. The assembly process, optical, and photoelectrical properties of the CdSe MDHs are thoroughly investigated. Several remarkable features of CdSe MDHs, including increased light absorption, efficient charge separation, and appropriate bandgap structure are confirmed. The MDHs significantly alleviate the sluggish kinetics of electron transfer in the quantum sized CdSe subunits (onset potential of 0.21 V vs RHE for MDHs; 0.4 V lower than their low‐dimensional building blocks), while the spatial nano‐confinement effect in the CdSe MDHs also assists the interfacial reaction kinetics to render them ideal photocatalysts for benzylamine oxidation (conversion > 99% in 4 h with a two times higher rate than simple mixtures). The results highlight opportunities for building MDHs from low‐dimensional building blocks with curvature‐complementary features and expand the application spectrum of low dimensional materials in artificial photosynthesis.

Section: Resultsmentioning

confidence: 99%

CdSe 1D/2D Mixed‐Dimensional Heterostructures: Curvature‐Complementary Self‐Assembly for Enhanced Visible‐Light Photocatalysis

Zhang

et al. 2021

Small

Part & Part Syst Charact

“…In particular, the direction‐dependent charge carrier transport in PbS NP supercrystals has been quantified. [ 268 ] To this end, the XCCA results have been correlated with the electronic properties of the same domains. The authors found a clear impact of supercrystal crystallinity on the electric conductivity.…”

Section: X‐ray Scattering Methodsmentioning

confidence: 99%

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

Schulz

Lokteva

Parak

et al. 2021

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...

“…[1][2][3][4][5][6][7][8] As a result, researchers have found that utilizing controlled self-assembly can lead to astounding new materials with exciting properties and unique function-alities. [9][10][11] This is not only restricted to isotropic spherical nanoparticles, which usually self-assemble into close-packed superlattices, but is especially true for anisotropic nanocrystals, which have shown to achieve even more complex superstructures and directional properties. [12][13][14] Controlled self-organization on the nanoscale has already been observed many years ago within the internal structure of BaSO 4 or rodlike particles of Ce IV minerals.…”

Section: Introductionmentioning

confidence: 99%

Titelbild: Binäre 3D‐Mesokristalle aus anisotropen Nanopartikeln (Angew. Chem. 2/2022)

et al. 2021

Binary mesocrystals offer the combination of nanocrystal properties in an ordered superstructure. Here, we demonstrate the simultaneous self-assembly of platinum and iron oxide nanocubes into micrometer-sized 3D mesocrystals using the gas-phase diffusion technique. By the addition of minor amounts of a secondary particle type tailored to nearly identical size, shape and surface chemistry, we were able to promote a random incorporation of foreign particles into a self-assembling host lattice. The random distribution of the binary particle types on the surface and within its bulk has been visualized using advanced transmission and scanning electron microscopy techniques. The 20-40 mm sized binary mesocrystals have been further characterized through wide and small angle scattering techniques to reveal a long-range ordering on the atomic scale throughout the crystal while showing clear evidence that the material consists of individual building blocks. Through careful adjustments of the crystallization parameters, we could further obtain a reverse superstructure, where incorporated particles and host lattice switch roles.