Composite graphitic nanolayers prepared by self-assembly between finely dispersed graphite oxide and a cationic polymer

Chemical flaking of graphite has been performed by reacting natural graphite with a strong oxidizing agent, NaClO3/HNO3. The formed hydrophilic, negatively charged graphite oxide (GO) colloids can be dispersed in water which allows the deposition of thin GO/cationic polymer (poly(diallyldimethylammoniumchloride, PDDA) multilayer films on a glass substrate by wet-chemical self-assembly. The feasibility of the charge-regulated layer-by-layer deposition is demonstrated by mutual charge titrations of the film-forming species. Visible-light spectroscopy revealed progressive growth of the film thickness with the number of deposition of steps, while XRD and AFM showed that partially exfoliated, highly anisometric (aspect ratio >50) graphite oxide platelet aggregates were deposited with an average thickness of the stacked graphite oxide platelets of 10 carbon layers (7.4nm). Reduction of multilayer assemblies of GO and PDDA on glass yielded a non-conductive turbostratic carbon nanofilm. The original, conductive graphite-like structure was restored by reduction with N2H4 and annealing at 400degreesC which, by gradual ordering of the carbon crystallites, caused a significant decrease in the resistivity. (C) 2004 Elsevier Ltd. All rights reserved.