No abstract

Two heteroarylene-vinylene donor-acceptor polymers, P(2,6-Py-V-EDOT) and P(2,5-Py-V-EDOT), containing vinylene-spaced simple donor (EDOT) and acceptor (pyridine) moieties, are presented. The central pyridine ring of the repeating unit is either 2,6-or 2,5-substituted, leading to different structural and electronic properties of the monomers. Polymers were obtained by either oxidative electropolymerization or Yamamoto coupling and fully characterized by NMR, UV-vis absorption, GPC, TGA, DSC, electrochemistry, and spectroelectrochemistry. Detailed ab initio computations have been performed for the monomers and model oligomers for analyzing their optical and electronic properties. GPC showed that isolated polymers obtained via Yamamoto poly coupling have low molecular weights, likely due to solubility issues. The electrochemical polymerizations led to p-and n-dopable polymers, with 2,5-Py-V-EDOT yielding more reversible n-doped process. The energetic positions revealed HOMO (-5.1 and -5.0 eV), LUMO (-3.4 eV), and narrow bandgap (1.6 and 1.7 eV) energies closely matching materials-design rules for optimized organic photovoltaic devices. Preliminary investigation in photovoltaic devices in combination with C 71 -PCBM afforded relatively modest power conversion efficiencies of ∼0.5% (AM 1.5G, 100 mW/cm 2 ), which were attributed to the low molecular-weight of the polymers accessible via the chemical route.

No abstract

Two families of thiophene‐based 2‐arylpyridines, in which aryl is phenyl and 2,4‐difluorophenyl, have been developed. The pyridine ring of the new compounds is substituted at the 4‐position with π‐conjugated electron‐rich and electron‐poor thiophene‐based fragments to tune the optical and energetic properties. The high‐yielding synthetic access, which consists of two sequential Suzuki coupling reactions, the first of which is completely regioselective, is of wide applicability and allows access to a large variety of derivatives. The absorption/emission and redox features, as well as the HOMO and LUMO energy levels, have been investigated; the results show that the optical and electronic properties can be tuned over a broad range. The diversity of the characteristics may be effectively exploited by using the thiophene‐substituted 2‐arylpyridines as ligands in cyclometalated sensitizers for dye‐sensitized solar cells and other optoelectronic applications.

Bio-impedance measurements can be used to detect and monitor several properties of living hard-tissues, some of which include bone mineral density, bone fracture healing or dental caries detection. In this paper a simple method and hardware architecture for hard tissue bio-impedance measurement is proposed. The key design aspects of such architecture are discussed and a commercial handheld ac impedance device is presented that is fully certified to international medical standards. It includes a 4-channel multiplexer and is capable of measuring impedances from 10 kOmega to 10 MOmega across a frequency range of 100 Hz to 100 kHz with a maximum error of 5%. The device incorporates several user interface methods and a Bluetooth link for bi-directional wireless data transfer. Low-power design techniques have been implemented, ensuring the device exceeds 8 h of continuous use. Finally, bench test results using dummy cells consisting of parallel connected resistors and capacitors, from 10 kOmega to 10 MOmega and from 20 pF to 100 pF, are discussed.