Growth and mechanism of CdS nanorods by microstructure analysis

Nanorods of II–VI semiconductor CdS are prepared from simple precursors by wet chemical method. The CdS nanorods are characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD studies showed that the crystal structure of the nanorods is in the hexagonal phase of CdS. The preferred orientation of (0 0 2) direction suggests that the nanorods of CdS is grown along (0 0 2) direction. The growth direction is further confirmed by microstructural analysis using HRTEM. Growth mechanism of the nanorods is explained on the basis of the population balance equation (PBE) model. The PBE model explains that the initially formed nanodots undergo oriented attachment (under ageing) along a particular direction having effective dipole moment (in the case of CdS it is (0 0 2) followed by coalescence leading to the smooth nanorods). This process takes place by ageing of the reaction solutions. The quasi-spherical nature of the particles results in a non-integral aspect ratio for the nanorods. Optical studies by UV–vis spectroscopy show a blue-shifted absorption at 493 nm because of the quantum confined excitonic absorption.