Figure 3.5 SEM images and schematic representation of SWNTs modification: (a) purified SWNTs, (b) SWNTs modified with PANI (after 300 cycles), and (c) possible mechanism of polymerization. Note: The images were changed with respect to the original use of pictures in the publication. Reprinted from Electrochem. Commun., 9, Wei, D., Kvarnström, C., Lindfors, T., and Ivaska, A., Electrochemical functionalization of single walled carbon nanotubes with polyaniline in ionic liquids, 206-210, Copyright (2007), with permission from Elsevier.Wei et al. synthesized PANI-gold composite (PANI:Au) nanoparticles in ionic liquid media for a nonvolatile memory device . The PANI:Au particles were synthesized by cyclic voltammetry in [EMIM][Tos] (tosylate) under acidic conditions. The resulting composite could directly be electrodeposited on modified ITO substrate to construct an active layer in the memory device, simplifying, therefore, the processing procedure considerably. The device was found to be stable in air, and it exhibited bistability and negative differential resistance. Reproducibility of these two parameters is of great importance in organic electronics. The obtained PANI:Au single-layer device was tested after 8 weeks and the device still exhibited sufficient current-voltage characteristics. Pringle et al. used [MEIM][Tf2N] (1-methyl-3-ethylimidazolium) in chemical synthesis of PPy and PTh. Different chemical oxidants (gold chloride, Fe tosylate, silver nitrate, and Fe(ClO4)3) were used as dopants . It was found that gold chloride suits best for fabrication of conducting polymer nanoparticles. The size of PTh and
PPy particles were from 100 to 500 nm with conductivity ranging from 1 to 3 mS cm-1. Recently Kim et al. made PPy nanostructures in the so-called magnetic IL . They used [BMIM][FeCl4], which is active under magnetic field and can be considered a paramagnetic compound . PPy particles were made by self-assembled method where [BMIM][FeCl4] was mixed with monomer and a magnetic field was applied resulting in PPy precipitate. Magnetic IL acted threefold: as dopant, catalyst, and solvent. The self-assembled particles were spheres of the size ranging from 50 to 100 nm with high electrical conductivities. Also in a recent paper Pringle et al. utilized [EMIM][Tf2N] for synthesis of PPy-gold and -silver composites with the use of gold chloride and silver nitrate . The use of these oxidants enabled a simple one-step fabrication of nanocomposites and IL assisted incorporation of metallic gold and silver into the polymer structure.