Role of Defects in Carbon Nanotube Walls in Deposition of CdS Nanoparticles from a Chemical Bath

Multiwall carbon nanotubes (MWCNTs), as-prepared and annealed in an inert atmosphere, have been used as templates for growth of CdS nanoparticles from an aqueous ammonium solution of cadmium chloride and thiourea. Transmission electron microscopy and Raman spectroscopy revealed that formation of CdS nanocrystals on the raw MWCNT surface proceeds markedly faster than on the annealed one. X-ray photoelectron spectroscopy showed a strong difference in the chemical state of the deposited CdS depending on the defect density in the MWCNTs. An interaction of Cd²⁺ ions and mixed Cd­(II) complexes with a defective graphene fragment was studied using density functional theory. The calculations indicated that, for attachment of Cd-containing species to the graphitic surface, defects with the dangling carbon bonds are needed. By combining the experimental and theoretical results, a model of CdS nucleation on the MWCNTs was proposed