Nearly every ionic solid consists of positively and negatively charged atoms, but in exotic materials called electrides, the negative "ion" is just an electron with no nucleus. Despite theoretical predictions of exciting chemical and optoelectronic properties of electrides in lower-dimensional forms, no electride has been synthesized or experimentally studied as a nanomaterial.
In work published in JACS, researchers in the Warren Group, in collaboration with colleagues in CHANL, synthesized and characterized a two-dimensional, 2D, form of an electride, 2D Ca2N. The synthesis was accomplished by exfoliating layered 3D Ca2N in organic solvent with ultrasonic power. The individual layers, or 2D flakes, are crystalline and have stoichiometry and bonding nearly identical to the 3D crystal.
Unlike other layered crystals, the interlayer gap of Ca2N is populated by free delocalized electron gas, which imparts very high electrical mobility. Because the 2D flakes are metallic with interband transitions that match calculations by DFT, the researchers suggest that the delocalized electron gas is preserved in the 2D system, making these electride nanomaterials and their free, anionic electrons attractive for a number of applications.