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 Ni2+/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.
Highlights
To control the growth of Ni(tto) as smaller objects, we have evaluated the use of biobased polyesters
Aconitic acid belongs to the products generally recognized as safe by the Food Drug Administration (FDA)
We have described the first nanoparticles of the conducting Ni(tto) polymer
Summary
Poly(nickel tetrathiooxalate), Ni(tto) (Figure 1), has an electrical conductivity in the 4 - 20 S∙cm−1 range. The conductivity value depends on the nature of the starting nickel salt, the solvent and the temperature used for their synthesis [1]. This conducting polymer has been processed as composites with poly(vinyl alcohol) [2], as self-assembled ultrathin films [3] or as coatings on CdS nanocrystals [4]. Yee [10] and Tkachov [12] have published improved and reproducible syntheses of respectively Ni(ett) and Ni(tto) which both exhibit enhanced electrical conductivity, and superior thermoelectric properties, thanks to the control of the synthesis parameters.
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