Synthesis and Characterization of the Thermoelectric Nickel Tetrathiooxalate Polymer as Nanoparticles

Abstract

Nanoparticles of the conductive coordination polymer Ni(tto) have been synthesized under mild conditions in the presence of bio-based polyesters or polyethylene glycol acting as growth controlling agents. With polyesters, aggregates of particles are observed whereas well dispersed nanoparticles are obtained with polyethylene glycol. Indeed, for a Ni 2+ /polyethylene glycol weight ratio of 0.031, transmission electron micrographs evidence dispersed particles exhibiting sizes in the 3-10 nm range. Infrared spectra for nanopowders show two CS stretching modes in the 1100-1190 cm −1 range, confirming the presence of the tetrathiooxalate ligand coordinated to the nickel center. The room-temperature electrical conductivity for the nanopowder prepared in the presence of polyethylene glycol is about 0.8 S•cm −1 , a decent value for tetrathiolate-based polymers. Finally, magnetic susceptibility measurements for well-dispersed Ni(tto) particles evidence a Curie-Weiss law in a large temperature range. Moreover, low temperatures measurement would confirm intra-or interchain interactions between nickel atoms within the Ni(tto) polymer chains.

Nanoparticles of Molecular Conductors and Superconductors: Progress Over the Last Ten Years

“…The conductivity of Ni(ett)/(BMIM)BF 4 nanoparticles [ 22 ] is much lower than the bulk polymer: [ 47a ] 10 –3 ‐10 –5 S.cm –1 and 1–50 Scm –1 , respectively. More encouraging is the conductivity of Ni(tto)/PEG (0.8 S.cm –1 ) [ 23 ] which is only slightly lower than the bulk material (30–50 S.cm –1 ), [ 47b ] thus deserving further measurements for the evaluation of ZT .…”