Solventless synthesis of nickel sulfide nanorods and triangular nanoprisms

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.