Molecular conductors as nanoparticles in the presence of long-chain alkyl imidazolium salts or amphiphilic molecules

Abstract

Nanoparticles of two molecule-based conductors, namely TTF·TCNQ and TTF[Ni(dmit)2]2, have been prepared in organic solution in the presence of ionic or nonionic species bearing a long-chain alkyl group, acting as growth-controlling agents. The size, morphology, and state of dispersion of the nanoparticles depended on the nature of the growth-controlling agent and the reaction temperature. In the presence of a long-chain alkyl-based ionic liquid at −50 °C, electron micrographs evidence that TTF·TCNQ nano-objects are frequently elongated, whereas TTF[Ni(dmit)2]2 nanoparticles are aggregated. In the presence of a neutral long-chain alkyl-based imine at room temperature, nanoparticles are spherical (mean diameter <20 nm) and well dispersed. Vibration spectra evidence that the amounts of charge transfer for TTF·TCNQ and TTF[Ni(dmit)2]2 as nano-objects are very similar to those for the same phases as bulk materials. According to the thermoanalytical investigations, the prepared nanoparticles are stable thermally up to approximately 200 °C, and their decomposition is generally a multi-step process. Their heat treatment results in various sulfur-containing volatiles (CS2, SO2, H2S); moreover, HCN is also detected in the case of nitrogen-containing molecules (TCNQ).