Ultrathin organically modified silica layer coated carbon nanotubes: Fabrication, characterization and electrical insulating properties

This paper describes the use of organically modified silica (ormosil) for the ultrathin nanoprecise coating of individual multiwall carbon nanotubes using a soft-chemistry approach. Hybrid organic/inorganic ormosil nanocoated carbon nanotubes were successfully prepared by in-situ deposition of 3-aminopropyltrimethoxysilane or Nmethylaminopropyltrimethoxysilane in an aqueous suspension by means of their electrostatic interactions with carboxylic group functionalized multiwall carbon nanotubes. The coating layer was found to have a uniform thickness of about 3 nm. The products were characterized by high-angle annular dark field scanning transmission electron microscopy, high-resolution transmission electron microscopy (HR-TEM), TEM/ energy-dispersive X-ray spectroscopy, TEM/electron energy loss spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and current- voltage measurements. The ormosil coatings demonstrated the favorable electrical insulating properties of individual multiw ll carbon nanotubes. We also show that the resistance of the insulating thin layer can be tuned by altering the substituents of alkylmethoxysilanes.