From Ultrathin Two-Dimensional Djurleite Nanosheets to One-Dimensional Nanorods Comprised of Djurleite Nanoplates: Synthesis, Characterization, and Formation Mechanism

Sn-doped ultrathin copper sulfide nanosheets of 209 ± 33 nm and nanoplates of 36.0 ± 5.9 nm were synthesized by pyrolyzing copper(II) acetylacetonate (Cu(acac) 2 ) in dodecanethiol in the presence of different amounts of SnCl 4 ·5H 2 O. The large nanosheets appeared in hexagonal and quasi-triangular shapes, while the small nanoplates presented mainly triangular shapes. Transmission electron microscopy (TEM) studies revealed that both nanosheets and nanoplates tended to form face-to-face stacking, which was further confirmed by X-ray diffraction studies. Such a self-assembling tendency became so strong for the small nanoplates that they formed one-dimensional (1D) self-assembled nanorods of 365 ± 145 nm. Atomic force microscopy studies revealed that the thickness of nanosheets was around 6.4−6.6 Å. The powder X-ray diffraction and high resolution TEM investigations demonstrated that the resultant two-dimensional (2D) nanocrystals are of monoclinic djurleite (Cu 31 S 16 ). Further investigations on different control samples revealed that Sn could partly replace Cu in forming lamellar supramolecular structures which actually acted as the precursors for the ultrathin 2D djurleite nanocrystals. Because of the excellent thermal stability and protective effects, the Sn-dodecanethiol complexes survived the pyrolysis of Cu(acac) 2 and preferentially attached on {100} facets of the resultant djurleite nanocrystals. Consequently, the growth of djurleite nanocrystals along the [100] direction was blocked, resulting in 2D Cu 31 S 16 nanocrystals. The dipole−dipole interaction along the [100] direction and the hydrophobic interaction between the nanoplates were the main driving force for the formation of 1D superstructures of the nanoplates.