Layer-by-layer deposition of cationic and anionic carbon nanotubes into thin films with improved electrical properties

Abstract

In this study, the electrical properties of carbon nanotubes (CNTs) assembled into different architectures using the layer-by-layer technique have been investigated. The CNTs were modified with either anionic water-soluble polyaniline blend poly(sodium 4-styrenesulfonate) (PANI-PSS) or cationic poly(diallydimethyl ammonium chloride) (PDADMAC) to form negatively charged CNT− and positively charged CNT+. PANI-PSS was synthesized by interfacial polymerization of aniline using PSS as template. The first of the three architectures studied was assembled by the LbL deposition of anionic CNT− and cationic CNT+ while the two others were prepared by the deposition of only 1 type of CNTs (CNT+ or CNT−) with an oppositely charged polyelectrolyte to form PDADMAC/CNT− and PANI-PSS/CNT+. The thickness and surface roughness of the three different films were characterized by atomic force microscopy (AFM) while the electrical and optical properties were measured using a four points probe setup and a UV–vis spectrophotometer, respectively. The dispersion of the CNTs using PANI-PSS as capping agent was the least efficient when compared to the PDADMAC leading to a lower adsorption on a charged substrate. Interestingly, the layer-by-layer deposition of the CNT−/CNT+ films had a slower growth but displayed a superior electrical conductivity when compared to the other two architectures.