Hexagonal Transition-Metal Chalcogenide Nanoflakes with Pronounced Lateral Quantum Confinement†
This work was supported by the German Research Council (Deutsche Forschungsgemeinschaft, HE 3543/18-1), The European Commission (FP7-PEOPLE-2009-IAPP QUASINANO, GA 251149 and FP7-PEOPLE-2012-ITN MoWSeS, GA 317451), The Office of Naval Research Global (N62909-13-1-N222), Air Force Office of Scientific Research (BAA-AFOSR-2013-0001-BRI-1), and the KRF Creative Research Initiative (2010-0018286) of Korea.
Graphical Abstract
Six-sided flakes: Transition-metal dichalcogenide nanoflakes of composition MX2 (where M=Ti, Zr and Hf; X=S and Se) grow preferentially in equilateral hexagons and exhibit a pronounced lateral quantum confinement. The hexagonal shape arises from the charge location at the edges and vertices and the resulting Coulombic repulsion.
Abstract
Transition-metal chalcogenide (TMC) nanoflakes of composition MX2 (where M=Ti, Zr and Hf; X=S and Se) crystallize preferentially in equilateral hexagons and exhibit a pronounced lateral quantum confinement. The hexagonal shape of octahedral (1T) TMC nanoflakes is the result of charge localization at the edges/vertices and the resulting Coulomb repulsion. Independent of their size, all nanoflakes have the MnX2n−2 stoichiometry and thus an unoxidized metal center which results in dopant states. These states become relevant for small nanoflakes and lead to metallic character, but for larger nanoflakes (>6 nm) the 2D monolayer properties dominate. Finally, coordination of Lewis bases at the nanoflake edges has no significant effect on the electronic structure of these species confirming the viability of colloidal synthetic approaches.
