Effect of sodium bromide salt on the buildup of consecutive MWCNTs film by electrostatic self-assembly

Abstract

Purified multiwalled carbon nanotubes (MWCNTs) were dispersed in poly sodium 4-styrenesulfonate (PSS) and polydiallyldimethylammonium (PDDA), respectively, solutions, where some of them were adsorbed on a CNT wall, providing a positive or negative charge on the CNT wall. The presence of surface charges on the CNTs then allowed a consecutive deposition of CNT via the electrostatic layer-by-layer method. The flexibility of the polyelectrolyte chain is one of the key parameters used for determining the ability of the chain to wrap around the nanotubes and thus affects the deposition morphology. This was controlled by changing the NaBr concentration. Analyses using UV- visible spectroscopy, ellipsometry, and scanning electron microscopy showed that the deposition rate of CNT-PSS increased as the NaBr concentration increased. The deposition rate of CNT-PDDA initially decreased as the NaBr concentration increased and it increased with further increasing NaBr concentration. The interaction between the CNT and PSS increased as the salt concentration increased from X-ray photoelectron spectroscopy analysis. However, the effect of NaBr on the interaction between CNT and PDDA was different from that of CNT-PSS. The unsaturated impurity peak of PDDA at 291 eV disappeared when the NaBr concentration was low and it appeared again as the NaBr concentration increased further. (c) 2007 The Electrochemical Society.