Layer-by-Layer Thin Films of Carbon Nanotubes
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0901-Ra05-41-Rb05-41.1
Layer-by-Layer Thin Films of Carbon Nanotubes Palumbo M.,a Lee K.U.,b Ahn B.T., b Suri A.,c Coleman K.,c Zeze D.,a Wood D.,a and Petty M.C.a a
School of Engineering and Centre for Molecular and Nanoscale Electronics, Durham University, South Road, Durham DH1 3LE, U.K. b Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, South Korea. c Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K. ABSTRACT Layer-by-layer films incorporating single-wall carbon nanotubes (SWNTs) with anionic or cationic coatings have been prepared. The process of self-assembly was monitored using the quartz microbalance technique, while the morphology of the resulting thin layers was studied with atomic force microscopy. A variety of different architectures have been built up. The dc conductivities of the thin films, in-plane and out-of-plane, were measured at room temperature and contrasted with reference architectures. The results show clearly that the incorporation of SWNTs into the multilayers resulted in electrically conductive thin films. INTRODUCTION The layer-by-layer (LbL) adsorption technique involves the assembly of oppositely charged layers of organic materials and can provide a 1 – 30 nm growth step for a bilayer. The starting point is normally a solid substrate with an electrically charged surface [1-3]. The adsorption of nano-objects (polymers, colloids, nanoparticles etc.) is carried out at a relatively high concentration and the solution pH or salt content can be used as an experimental parameter to control the degree of ionization of the polymer chains [4, 5]. Following each adsorption step, a number of ionic groups remain exposed at the interface with the solution, resulting in a reversal of the initial surface charge. The substrate is then exposed to a solution containing an oppositely charged nano-object. Again, a layer is adsorbed and the surface charge restored. By alternating these two steps, multilayer structures may be built up. Carbon nanotubes are one of the most promising classes of materials for nanotechnology applications [6, 7]. Possible uses include: chemical sensors, field-emission flat-panel displays, conductive plastics, high-performance fibres, advanced composite materials, batteries and materials for hydrogen storage [7]. In this paper, we explore the use of the LbL technique to build up thin film architectures incorporating single wall nanotubes (SWNTs). The deposition method suggests a means to control the agglomeration tendency of the nanotubes [8, 9]. We have used an appropriate selection of surfactants with opposite electrical charges to prepare suitable nanotube dispersions. These were then incorporated into more complex and organized multilayer architectures. The deposition characteristics of the thin layer assemblies and their electrical behaviour are reported.
0901-Ra05-41-Rb05-41.2
EXPERIMENTAL DETAILS Poly(ethyleneimine), PEI (Mw = 25,000), and poly(acrylic acid), PAA (Mw = 400,00
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