Shape- and phase-controlled ZnS nanostructures and their optical properties

• Stacking faults were observed for ZnS nanocrystals with the size of ∼5 nm.
• Nanotwinning structures and stacking faults were observed in ZnS nanorod.
• Microstructure defects were found to be formed randomly for nanocrystals and nanorods.
• The 1LO phonon mode exhibits a red-shift of 6 cm−1 as the particle size increases from 5 to 15 nm.

Single-crystalline ZnS nanoparticles with a zinc-blende crystal structure have some microdefects such as stacking faults and nanotwins. In contrast, ZnS nanorods have a wurtzite crystal structure, which grows along the [0 0 0 1] direction, although some nanorods display the intergrowth of a minor zinc-blende phase and the major wurtzite phase, which forms stacking faults or zinc-blende/wurtzite ZnS nanotwins. Raman spectroscopy measurements reveal surface phonons and longitudinal optical phonons in the nanoparticles, nanorods and doublet phonons that are associated with the transversal optical phonons of the A1 and E1 modes in only the nanorods. The first-order longitudinal optical phonon mode exhibits a blueshift of 6 cm−1 when the particle size increases from 5 to 15 nm, but there is no shift in the range of 15–30 nm because of quantum confinement and microdefects.

(a) TEM images of the nanorods, the HRTEM images for the lower (b) and the upper (c) part of the rod in (a).Figure optionsDownload as PowerPoint slide