title: Two-Dimensional Colloidal Nanocrystals.
abstract: In this paper, we review recent progress on colloidal growth of 2D nanocrystals. We identify the four main sources of anisotropy which lead to the formation of plate- and sheet-like colloidal nanomaterials. Defect-induced anisotropy is a growth method which relies on the presence of topological defects at the nanoscale to induce 2D shapes objects. Such a method is particularly important in the growth of metallic nano-objects. Another way to induce anisotropy is based on ligand engineering. The availability of some nanocrystal facets can be tuned by selectively covering the surface with ligands of tunable thickness. Cadmium chalcogenides nanoplatelets (NPLs) strongly rely on this method which offers atomic control in the thinner direction, down to a few monolayers. Two-dimensional objects can also be obtained by post or in situ self-assembly of nanocrystals. This growth method differs from the previous ones in the sense that the elementary objects are not molecular precursors and is a common method for lead chalcogenide compounds. Finally, anisotropy may simply rely on the lattice anisotropy itself as it is common for rod-like nanocrystals. Colloidally grown transition metal dichalcogenides (TMDC) in particular result from such process. We also present hybrid syntheses which combine several of the previously described methods and other paths, such as cation exchange, which expand the range of available materials. Finally, we discuss in which sense 2D objects differ from 0D nanocrystals and review some of their applications in optoelectronics, including lasing and photodetection, and biology.
authors.affiliation: Laboratoire de Physique et d'Étude des Matériaux, PSL Research University, CNRS UMR 8213, Sorbonne Universités UPMC Université Paris 06, ESPCI Paris, 10 rue Vauquelin, 75005 Paris, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Nasilowski
authors.affiliation: Institut Lumière-Matière, CNRS UMR5306, Université Lyon 1, Université de Lyon , 69622 Villeurbanne CEDEX, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Mahler
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lhuillier
authors.affiliation: Laboratoire de Physique et d'Étude des Matériaux, PSL Research University, CNRS UMR 8213, Sorbonne Universités UPMC Université Paris 06, ESPCI Paris, 10 rue Vauquelin, 75005 Paris, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Ithurria
authors.affiliation: Laboratoire de Physique et d'Étude des Matériaux, PSL Research University, CNRS UMR 8213, Sorbonne Universités UPMC Université Paris 06, ESPCI Paris, 10 rue Vauquelin, 75005 Paris, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Dubertret