Solution-phase catalytic synthesis, characterization and growth kinetics of Ag2S–CdS matchstick-like heteronanostructures

Abstract

A facile catalytic growth route was developed for the low-temperature solution synthesis of Ag2S-CdS matchstick-like heteronanostructures in oleylamine, which are composed of a Ag2S spherical head and a CdS rod-like stem. Ag2S nanoseeds acted as an effective catalyst for the growth of CdS nanorods and remained at the tip of the resultant nanorods, leading to the formation of Ag2S-CdS heterostructures with a matchstick shape. The diameter of the Ag2S heads and the length of the CdS stems could be easily controlled by varying the molar ratios of the Ag/Cd precursors. The differential scanning calorimetry (DSC) and variable-temperature X-ray diffraction (XRD) studies confirmed that Ag2S catalytic seeds underwent a phase change, that is, they were in a high-temperature superionic conducting cubic structure during the CdS nanorod growth and then converted to a low-temperature monoclinic crystal structure as the reaction was cooled to room temperature. The influence of synthetic temperature on the product morphology was investigated and the morphological evolution at different growth stages was monitored using transmission electron microscopy (TEM). Furthermore, the growth kinetics of the Ag2S-CdS matchstick-like heteronanostructures, including the dissolution, nucleation and growth of CdS within the Ag2S catalyst, was reasonably discussed on the basis of the structural characteristics of the superionic cubic Ag2S catalyst and the low solubility of CdS in Ag2S derived from the Ag2S-CdS binary phase diagram.