Thermoelectric figure of merit of tau-type conductors of several donors

Dimensionless thermoelectric figure of merit $ZT$ is investigated for two-dimensional organic conductors $\tau-(EDO-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, $\tau$-(EDT-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$and$\tau$-(P-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$ ($y \le 0.875$), respectively. The $ZT$ values were estimated by measuring electrical resistivity, thermopower and thermal conductivity simultaneously. The largest $ZT$ is 2.7 $\times$ 10$^{-2}$ at 155 K for $\tau-(EDT-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, 1.5 $\times$ 10$^{-2}$ at 180 K for $\tau-(EDO-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$ and 5.4 $\times$ 10$^{-3}$ at 78 K for $\tau-(P-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, respectively. Substitution of the donor molecules fixing the counter anion revealed EDT-S,S-DMEDT-TTF is the best of the three donors to obtain larger $ZT$.Comment: proceedings of ISCOM 2009 (to be published in Physica B

Synthesis of some new electron π-donors containing methoxy groups

The synthesis of some new electron π-donors carrying four or two methoxy groups is described. The precursor 5,6-dimethoxy-5,6-dihydro[1,3]dithiolo[4,5- b] [1,4]dithiin-2-thione was synthesized and by coupling reactions the symmetrical 5,6,5′,6′-tetramethoxy-5,6,5′,6′-tetrahydro- [2,2′]bi[[1,3]dithiolo[4,5-b][1,4]dithiinylidene] and unsymmetrical 5,6-dimethoxy-5,6,5′,6′-tetrahydro-[2,2′]bi[[1,3]-dithiolo[4, 5-[1,4]dithiinylidene], 2-(5,6-dimethoxy-5,6-dihydro-[1,3]dithiolo[4,5-b][1,4] dithiin-2-ylidene)-5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]-dioxine and (5,6-dimethoxy-5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dithiin-2-ylidene)-6, 7-dihydro-5H-[1,3]dithiolo[4,5-6][1,4]dithiepine donors were prepared. They have been characterized spectroscopically and their redox potentials determined using cyclic voltammetry

Laser-induced localized formation of silver nanoparticles on chitosan films: Study on particles size and density variation

Wepresent the in situ localized formation of silver nanoparticles in chitosan films by pulsed UV laser irradiation, as a result of the photoreduction of the silver nitrate precursor loaded throughout the volume of the polymer. TheUVpulsed irradiation is also found to be responsible for the photofragmentation of the previously formed nanoparticles, leading to their average size reduction as the number of pulses increases. In fact, their diameter changes from 3c 150 to 3c 30 nmfor irradiation with 5 to 200 pulses, respectively. After irradiation the formation of nanoparticles continues for several days, since the already formed nanoparticles act as seeds for the reduction of the unreacted precursor. Indeed, few weeks after irradiation, the chitosan films present a metallic mirror-like appearance on the previously irradiated areas, as they are fully covered by silver. Taking advantage of all these simultaneous mechanisms, and controlling the number of pulses and elapsed time after irradiation, Ag nanoparticles of specific size can be formed in situ on desired areas of the film. Through this process is envisioned the fabrication of nanocomposites with functional properties

Some unsymmetrical nickel 1,2-dithiolene complexes as candidate materials for optics and electronics

The unsymmetrical complexes Ni(tmedt)(dddt), Ni(dpedt)(dddt), Ni(tmedt)(dmit), and Ni(dpedt)(dmio) (where tmedt is trimethylene-ethylenedithiolate, dddt is 5,6-dihydro-1,4-dithin-2,3-dithiolate, dmit is 1,3-dithiol-2-thione-4,5-dithiolate, dpedt is diphenyl-ethylenedithiolate, and dmio is 1,3-dithiol-2-one-4,5-dithiolate) were prepared and their structural and physical properties investigated. The results were compared with those obtained from similar unsymmetrical and the corresponding symmetrical complexes. The new complexes were found to be stable in air and exhibit the necessary structural and physical properties in order to be candidate materials for optical and electronic devices. © 2008 Elsevier Masson SAS. All rights reserved

Effect of trifluoroacetic acid on the properties of polyvinyl alcohol and polyvinyl alcohol-cellulose composites

Highly stretchable polyvinyl alcohol (PVA) films with a strain at break of around 700% were obtained from solutions in trifluoroacetic acid (TFA). Structural and chemical analysis by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (ATR-FTIR) showed that TFA is retained by PVA via hydrogen bonds between the carboxylic acid groups and the hydroxyl groups of the polymers causing a strong plasticizing effect. Additionally, composites of PVA with cellulose could be developed using TFA as common solvent. The morphological and mechanical properties of the polymer composites could be accurately tuned by modifying the relative concentrations of the two polymers. Data from water adsorption isotherms and wetting measurements indicated that the presence of trifluoromethyl groups in PVA render the composite films relatively hydrophobic. © 2015 Elsevier B.V

Investigation of the electro-spinnability of alginate solutions containing gold precursor HAuCl4

Alginate nanofibers with an average diameter of 75 nm have been prepared by the electrospinning process. In addition, the spinnability of the solutions in the presence of the gold precursor HAuCl4 was investigated. At low concentrations of HAuCl4 well-formed nanofibers were produced, whereas as its concentration increases the nanofibrous mats present an increased number of bead-like defects. Herein, the in situ preparation of gold nanoparticles (Au NPs) is discussed since sodium alginate (SA) acts as the reducing agent and a mechanism is proposed in order to explain the bead-effect as well as the surface morphology of the alginate fibers decorated with Au NPs. © 2016 Elsevier Inc