Infrared and Raman investigation of carbon nanotube-polyallylamine hybrid systems

Abstract

Non-covalent functionalization of carbon nanotubes (CNTs) by polymers or aromatic systems is a rapidly emerging field. Its importance originates in the possibility of combining special (optical, electric, or dispersive) properties of the added molecules with the mechanical stability of nanotubes. A special application is to use the polymers as interfaces between nanotubes and metallic nanoparticles ("molecular glue"). Crucial to all applications is an experimental tool to characterize the interaction strength between the nanotubes and the associated species. In this paper, we study hybrids of single-walled nanotubes (SWNT) and polyallylamine obtained from poly(allylamine hydrochloride) (PAH) at high pH. We use attenuated total reflection (ATR) spectroscopy and Raman spectroscopy to understand how polyallylamine covers the surface of the nanotubes. The interaction of the evanescent field on the surface of the nanotube with the vibrations of the adsorbed species invokes surface selection rules and, hence, surface-attenuated infrared absorption (SAIRA). Raman spectra prove diameter-selective solubilization of the polymer-covered nanotubes. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.