Direct Synthesis of Carbon–Molybdenum Carbide Nanosheet Composites via a Pseudotopotactic Solid-State Reaction

We report the solid-state reaction of MoO₂ nanosheets, obtained from the soft-chemical delamination of Na_0.9Mo₂O₄, into metallic Mo₂C single layers that constitute a new family of versatile carbide nanosheets. This so-called pseudotopotactic reaction, i.e., conversion from nanosheet to nanosheet, is aided by the use of cationic polymers as binders for the film growth based on electrostatic self-assembly. Compared to Mo₂C in the bulk form, 2D anisotropic Mo₂C sheets having a larger surface-area-to-volume ratio are of significant use in potential electrochemical applications, and it is also worth noting that the thickness of Mo₂C sheets can be controlled in the nanometer range by altering the stacking number of the precursor nanosheets

Ligancy-Driven Controlling of Covalency and Metallicity in a Ruthenium Two-Dimensional System

The homopolar network and conjugation in <i>d</i>-block single elements can materialize a highly anisotropic and robust structure of a noble-metal system. Here, we have prepared ruthenium (Ru) atomic monolayers of a nonmetallic hexagonal lattice, and determined their layering scheme and metallization. The two-dimensional (2D) network is retained at the first stacking of the monolayer, while maintaining the nonmetallic features. We find out that the <i>atop</i> (AA) related stacking structure of bilayered Ru nanosheets occurs due to the ligancy-driven covalency, and the inception of the metallic electronic states is from trilayered stacking. These results indicate that the metallic states can be separated from covalent-bonding linkage and unpaired electrons in <i>spd</i> hybrid orbital systems. Our approach enables the molecular structure of noble-metal atoms to be induced via controlling the ligancy of <i>d</i>-block atomic bonds