Copper(II)-mediated layer-by-layer assembly of viologenthiol-functionalized carbon nanotube hybrid multilayers: preparation, characterization, morphology, and electrochemical properties

The metal-mediated self-assembly of coordination polymers, building blocks, and metal-organic frameworks has been widely used to construct multifunctional novel materials on the molecular level. Here, we developed this technique to build up multilayers of functionalized carbon nanotubes on the basis of both intermolecular electrostatic and coordinative interactions. Positively charged electroactive viologenthiol (VSH) was first immobilized on multiwalled carbon nanotubes (MWNTs) to form MWNT-VSH hybrids with a relative content of ∼9% by weight. Field emission transmission electron microscopy images revealed that the VSH molecules randomly covered the surfaces of MWNTs with a thickness of 1 to 2 nm. Then, the MWNT-VSH hybrids were used as nanoscale multidentate "ligands" (linkers) to construct metal-mediated multilayers with the use of CuAc(2) as the connectors by the layer-by-layer (LBL) method. The assembly process was monitored by absorption and X-ray photoelectron spectroscopy as well as scanning electron and atomic force microscopy after each assembly of Cu(II) ions and MWNT-VSH hybrids. Finally, the electrochemical behaviors of the viologens in the MWNT-VS/Cu LBL multilayers were investigated.