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31. Monolayer-to-thin-film transition in supramolecular assemblies: the role of topological protection† †Electronic supplementary information (ESI) available: AFM images, STM images, TEM diffraction and acTEM images, multislice TEM image simulation details, and theoretical derivations of acTEM image reconstruction. See DOI: 10.1039/c7nr03588h. All data presented in this paper are available at http://wrap.warwick.ac.uk/90210

Author

Laker, Zachary P. L., Marsden, Alexander J., De Luca, Oreste, Pia, Ada Della, Perdigão, Luís M. A., Costantini, Giovanni, and Wilson, Neil R.

Subjects
Chemistry
Abstract

An innovative combination of TEM and STM sheds new insight into the growth of organic layers and reveals the importance of topology in controlling the transition from two- to three-dimensional structure., The ability to control the transition from a two-dimensional (2D) monolayer to the three-dimensional (3D) molecular structure in the growth of organic layers on surfaces is essential for the production of functional thin films and devices. This has, however, proved to be extremely challenging, starting from the currently limited ability to attain a molecular scale characterization of this transition. Here, through innovative application of low-dose electron diffraction and aberration-corrected transmission electron microscopy (acTEM), combined with scanning tunneling microscopy (STM), we reveal the structural changes occurring as film thickness is increased from monolayer to tens of nanometers for supramolecular assembly of two prototypical benzenecarboxylic acids – terephthalic acid (TPA) and trimesic acid (TMA) – on graphene. The intermolecular hydrogen bonding in these molecules is similar and both form well-ordered monolayers on graphene, but their structural transitions with film thickness are very different. While the structure of TPA thin films varies continuously towards the 3D lattice, TMA retains its planar monolayer structure up to a critical thickness, after which a transition to a polycrystalline film occurs. These distinctive structural evolutions can be rationalized in terms of the topological differences in the 3D crystallography of the two molecules. The templated 2D structure of TPA can smoothly map to its 3D structure through continuous molecular tilting within the unit cell, whilst the 3D structure of TMA is topologically distinct from its 2D form, so that only an abrupt transition is possible. The concept of topological protection of the 2D structure gives a new tool for the molecular design of nanostructured films.

Published
2017

43. Quantitative 3D analysis of huge nanoparticle assemblies† †Electronic supplementary information (ESI) available.CCDC 1417516–1417520 contain the supplementary crystallographic data for this paper. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5nr06962a Click here for additional data file

Author

Zanaga, Daniele, Bleichrodt, Folkert, Altantzis, Thomas, Winckelmans, Naomi, Palenstijn, Willem Jan, Sijbers, Jan, de Nijs, Bart, van Huis, Marijn A., Sánchez-Iglesias, Ana, Liz-Marzán, Luis M., van Blaaderen, Alfons, Joost Batenburg, K., Bals, Sara, and Van Tendeloo, Gustaaf

Subjects
Chemistry
Abstract

A new reconstruction approach for electron tomography is proposed, enabling a detailed 3D analysis of assemblies with as many as 10 000 particles., Nanoparticle assemblies can be investigated in 3 dimensions using electron tomography. However, it is not straightforward to obtain quantitative information such as the number of particles or their relative position. This becomes particularly difficult when the number of particles increases. We propose a novel approach in which prior information on the shape of the individual particles is exploited. It improves the quality of the reconstruction of these complex assemblies significantly. Moreover, this quantitative Sparse Sphere Reconstruction approach yields directly the number of particles and their position as an output of the reconstruction technique, enabling a detailed 3D analysis of assemblies with as many as 10 000 particles. The approach can also be used to reconstruct objects based on a very limited number of projections, which opens up possibilities to investigate beam sensitive assemblies where previous reconstructions with the available electron tomography techniques failed.

Published
2015