Quantifying Angular Correlations between the Atomic Lattice and the Superlattice of Nanocrystals Assembled with Directional Linking

Abstract

We show that the combination of X-ray scattering with a nanofocused beam and X-ray cross correlation analysis is an efficient means for the full structural characterization of mesocrystalline nanoparticle assemblies with a single experiment. We analyze several hundred diffraction patterns of individual sample locations, i.e. individual grains, to obtain a meaningful statistical distribution of the superlattice and atomic lattice ordering. Simultaneous small-and wide-angle X-ray scattering of the same sample location allows us to determine the structure and orientation of the superlattice as well as the angular correlation of the first two Bragg peaks of the atomic lattices, their orientation with respect to the superlattice, and the average orientational misfit due to local structural disorder. This experiment is particularly advantageous for synthetic mesocrystals made by the simultaneous self-assembly of colloidal nanocrystals and surfacefunctionalization with conductive ligands. While the structural characterization of such materials has been challenging so far, the present method now allows correlating mesocrystalline structure with optoelectronic properties. Mesocrystals (MC) are three-dimensional arrays of iso-oriented single-crystalline particles with an individual size between 1 -1000 nm. [1][2][3][4][5] Their physical properties are largely determined by structural coherence, for which the angular correlation between their individual atomic lattices and the underlying superlattice of nanocrystals (NC) is a key ingredient. 1,2 Colloidal NCs stabilized by organic surfactants have been shown to pose excellent building blocks for the design of synthetic MCs with tailored structural properties which are conveniently obtained by self-assembly of NCs from solution on a solid or liquid substrate by exploiting ligand-ligand 3 interactions. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Typically, the utilized ligands consist of wide-gap, bulky hydrocarbons which render the MCs insulating. [26][27][28][29][30][31][32][33] MCs obtained in this way exhibit average grain sizes of ~150 µm 2 , which enables a detailed characterization by electron and/or X-ray microscopy. 34 Since the optoelectronic properties of PbS NC ensembles bear many opportunities for applications in solar cells or photodetectors, a number of ligand exchange procedures with small organic or inorganic molecules as well as single atom passivation strategies have been developed, all of which greatly increase the carrier mobilities within the SL of NCs. 28,33,[35][36][37][38][39][40][41][42][43][44] Due to the short interparticle spacing imposed by these ligands, structural coherence is mostly lost in such superlattices, but in rare cases it has been demonstrated that significant long-range order and even mesocrystallinity can be preserved. 25,35,45 However, a persisting problem of these protocols is that they are prone to introduce defects in the superlattice structure with some degree of granularity and signifi...

Pressure-Stimulated Supercrystal Formation in Nanoparticle Suspensions

“…[6][7][8][9][10][11] The transition of NP in solution into crystalline structures has already been realized in various ways. 3,[12][13][14][15] Self-assembly and crystallization of NPs is generally a complex process, [16][17][18][19][20][21] usually based on the controlled evaporation or precipitation of the NP-building blocks by slow addition of a non-solvent. 3,22 These processes have to be slow in order to achieve homogenous crystallization conditions for obtaining high-quality supercrystals.…”

Highly Efficient Degradation of Tobacco Specific N‐Nitrosamines by TiO2 Mesocrystals with Robust and Tailored Microporous Structure

“…Furthermore, mesocrystals have remarkable versatility in chemical compositions compared with zeolites, and would hold a variety of promising properties. Mesocrystals also permit the advantages of single crystals as well as large surface area, making them more promising in the applications of catalysis, sensing and energy storage and conversion . In our and other group's previous work, TiO 2 mesocrystals with different phase and morphology were synthesized, which exhibited superior performance in energy storage and conversion, sensing and photocatalysis .…”

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

“…[ 4–7 ] However, experimental proof for a correlation between structure and charge transport in NC SLs is still pending. Previous experimental research on NC SLs has either focused solely on the process of self‐organization and structural order [ 8–13 ] or, in separate studies, on charge transport, and electronic properties. [ 14–19 ] In order to reveal potential transport anisotropy, a correlated investigation of charge transport and structural order on the same NC SL is required.…”