Physical properties of a molecular conductor (BEDT-TTF)2I3 nanohybridized with silicananoparticles by dry grinding

Abstract

The dry grinding of a mixture of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and silica nanoparticles has produced powdery (BEDT-TTF)–silica nanocomposites. The (BEDT-TTF)–silica nanocomposites are readily doped with iodine in hexane dispersion to give powdery nanocomposites of (BEDT-TTF)₂I₃–silica. XRD and TEM measurements suggest that (BEDT-TTF)₂I₃ in the nanocomposite exists as shell layers of core-shell-type nanoparticles and as nanometre-sized crystals incorporated into hollow sites of aggregated silica nanoparticles. Magnetic susceptibility measurements reveal that the nanocomposites accompanied a large number of Curie spins attributable to surface molecules of the core-shell-type nanoparticles. The nanocomposites show a magnetic susceptibility change corresponding to the metal-insulator transition of α-(BEDT-TTF)₂I₃ in a broad temperature range of 110–140 K, which is attributed to the properties of the nanocrystalline components. Doping in diethyl ether dispersion leads to higher amounts of the nanocrystalline component being obtained. The doping of (BEDT-TTF)–silica nanocomposites by dry grinding produces a paramagnetic powder containing amorphous (BEDT-TTF)₂I₃, which possesses a Curie spin concentration of 50%. The effects of annealing on these nanocomposites are investigated. The electrical conductivity of the compaction pellets of (BEDT-TTF)–silica nanocomposites is enhanced by iodine doping to reach approximately 10⁻⁶ S cm⁻¹, but the value is much lower than that of the bulk crystals (10¹ S cm⁻¹).