One-pot synthesis of carbon nanotube/zinc sulfide heterostructures: Characterization and effect of electrostatic interaction on the optical properties

Abstract

An aqueous route based on electrostatics for preparing heterostructures from carbon nanotubes (CNT) and Zinc Sulfide doped with manganese (ZnS:Mn) is demonstrated. This was achieved by one-pot synthesis of negatively charged multiwalled carbon nanotubes and positively charged ZnS quantum dots, in a reaction driven by the electrostatic interaction between the binary components. The structural and optical properties of the heterostructures were characterized by particle size, zeta potential, x-ray diffraction, transmission and scanning electron microscopy, and photoluminescence measurements. A size-restriction effect of the CNTs on the growth of the ZnS nanoparticles during synthesis was observed, particle sizes of the prepared composites were smaller with higher amounts of CNT. Remarkably, all ZnS:Mn/CNT composites showed a blue shift of in the excitation spectra compared to ZnS:Mn only. Further experiments attributed the blue shift to an increased band gap of the ZnS:Mn, originating from an effective electrostatic interaction between the CNT and the attached ZnS:Mn. This effect was indicative of an intimate contact between the CNTs and the ZnS:Mn which was affirmed by images obtained from Transmission Electron Microscopy as well. Composites with such controlled morphology between the binary components are relevant in the fabrication of inorganic nanomaterial-carbon nanotube heterostructures, directed towards applications in optoelectronics.