Solventless synthesis of monodisperse Cu2S nanorods, nanodisks, and nanoplatelets

Cu2S nanocrystals with disklike morphologies were synthesized by the solventless thermolysis of a copper alkylthiolate molecular precursor. The nanodisks ranged from circular to hexagonal prisms from 3 to 150 nm in diameter and 3 to 12 nm in thickness depending on the growth conditions. High resolution transmission electron microscopy (HRTEM) revealed the high chalcocite (hexagonal) crystal structure oriented with the c-axis ([001] direction) orthogonal to the favored growth direction. This disk morphology is thermodynamically favored as it allows the extension of the higher energy {100} and {110} surfaces with respect to the {001} planes. The hexagonal prism morphology also appears to relate to increased C-S bond cleavage of adsorbed dodecanethiol along the more energetic {100} facets relative to {001} facets. Monodisperse Cu2S nanodisks self-assemble into ribbons of stacked platelets. This solventless approach provides a new technique to synthesize anisotropic metal chalcogenide nanostructures with shapes that depend on both the face-sensitive thermodynamic surface energy and the surface reactivity.