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.

Organic monolayer protected Cu2S nanorods, 4 nm in diameter and 12 nm long, were synthesized using a novel solventless synthetic approach. Thermolytic degradation of a copper thiolate precursor at temperatures ranging from 140 to 200 degrees C produces Cu2S nanorods. Higher temperatures promote isotropic growth of spherical nanocrystals. X-ray diffraction and high-resolution TEM reveal that the nanorods exhibit a hexagonal Cu2S crystal structure, which in the bulk is ferroelectric. The appropriate reaction conditions produce nanorods that are size and shape monodisperse and organize into smectic superlattices. The extent of superlattice ordering and the appearance of extended strands of nanorods provide evidence for strong dipole-dipole coupling between Cu2S nanorods.

Organic monolayer-coated rhombohedral NiS (millerite) nanorods and triangular nanoprisms were synthesized using a solventless thermolytic decomposition of nickel thiolate precursors in the presence of octanoate. The size and shape distributions are relatively narrow, with nanorod lengths that depend on the growth conditions, ranging from 15 to 50 nm and typically with aspect ratios of approximately 4. For example, a typical procedure yields nanorods 33.9 ± 8.6 nm long and 8.11 ± 1.6 nm wide. The approach also yields triangular nanoprisms under some reaction conditions with nearly a 1:1 ratio of nanorods to nanoprisms. FTIR spectra reveal that octanoate serves as a capping ligand that controls nanorod growth. X-ray diffraction (XRD) shows that the primary reaction byproduct in the synthesis is colloidal Ni3S4 in the form of misshapen needles and particulates. High-resolution transmission electron microscopy (HRTEM) confirm that the well-defined nanorods and triangular nanoprisms are composed solely of rhombohedral NiS (millerite) grown preferentially in the [110] direction.

Orthorhombic Bi2S3 (bismuthinite) nanorods and nanowires are synthesized by the solventless thermolysis of bismuth alkylthiolate precursors. Reactions carried out in air at ∼225 °C in the presence of a capping ligand species, octanoate, produce high aspect ratio (>100) nanowires. Lower aspect ratio nanowires (∼7) are produced by the same approach with the addition of elemental sulfur at lower reaction temperature (∼160 °C). Both the nanowires and nanorods are oriented with their long axes in the [002] crystallographic direction. Higher reaction temperatures (∼250 °C) produce crossed nanowire networks, or fabrics, with highly oriented growth as a result of heterogeneous nanowire nucleation and epitaxial elongation off the surface of existing wires.

The self-assembly of sterically stabilized colloidal copper sulfide nanodisks, 14-20 nm in diameter and 5-7 nm thick, was studied. The nanodisks were observed by electron microscopy and small-angle X-ray scattering to form columnar arrays when evaporated as thin films from concentrated dispersions. These superstructured nanomaterials might give rise to technologically useful properties, such as anisotropic electrical transport and electrorheological and optical properties.